Ⅰ.
The system of legally secured portions is to help the person entitled to legally secured portions to keep its livelihood even after the death of the inheritee, to protect the person entitled to legally secured portions in order that it may expect to inherit the property from the family community, and to secure the equality between coheirs as the persons entitled to legally secured portions. Such function is in line with clause 1 of article 36 of the Constitution of the Republic of Korea, i.e., the concrete actualization of the constitutional protection of family life. Accordingly, the system of legally secured portions is not contrary to the Constitution, and moreover the abolition of the system is contrary to clause 1 of article 36 of the Constitution; to wit, it is unconstitutional. As the case stands, the system of legally secured portions and the system of legal inheritance are on the same legal basis. To put it another way, the system of legally secured portions functions as a counterbalance to what the civil law permits inheritees to freely make wills and to extensively dispose of their properties. Altogether, the system was established on purpose to protect interest which the persons entitled to legally secured portions have in relation to legal inheritance.
Even at present, most of countries have regulations equivalent to the system of legally secured portions though their legal structures are different from each other. This fact verifies that the system has rightfully functioned to protect persons entitled to legally secured portions. However, what should not be overlooked is that average life span has been extended and thus population structure has been changed to the aging society. To be specific, the system should be continuously reevaluated and reformed in consideration of social changes. In addition, the system needs to be prudently operated under the principle of ‘trust and sincerity (Civil Law article 2)’ so as to prevent the cases where the claim for return for legally secured portions is exercised very unfairly, as well as to realize justice and equity.

Ⅱ.
This dissertation laid emphasis on the formative effect of the claim of return for legally secured portions from a theoretical standpoint which understands the legal nature of the claim of return for legally secured portions to be ‘Gestaltungsrecht’(German for the right, the holder of which is permitted to unilaterally cause changes in one's and/or other party's legal relationship). When the claim of return for legally secured portions is exercised, a gift or a testamentary gift that infringes on legally secured portions will be nullified retrospectively, as a result of which the right holder of the legally secured portions will acquire a real right-like claim as well as the claim of return for unjust enrichment. In terms of the realization of ownership, the application of the provisions stipulating the real right-like claim and the claim of return for unjust enrichment concur. In ordinary cases the right holder of legally secured portions will recover the principal thing through the exercise of the claim for return of one's property(Korean Civil Law article 213). However for the purpose of settling debt, only the law on unjust enrichment will apply.
In other words, from such a viewpoint like the one in this dissertation, in respect of the legal relations between the right holder of the legally secured portions and other party after the former’s exercise of the claim of return, the return of the principal thing is regulated by the provisions concerning the real right-like claim and the claim of return for unjust enrichment, whereas interest intermediation issues incidental to return (such as the return of profits attained from the object, liability for the loss or damage of object, the redemption of the expense incurred by the other party) are to be regulated by the provisions on the return for unjust enrichment. As a result the Civil Law can be said to a unified and comprehensive regulatory system of law, showing no defects in this respect.
However if the claim of return for legally secured portions is understood as ‘Gestaltungsrecht’, Civil Law would have defects of the provisions for limiting the prospective effect towards the bona-fide third party in terms of the return of legally secured portions, and this would in turn undermine the safety and stability of transactions. Therefore it would necessitate the protection of the bona-fide third party thorough the means of analogizing the value assessment underlying the provisions on the protection of the bona-fide third party.

Ⅲ.
The prevalent view in Korea on the claim of return for secured portions was that it is not a right which is strictly personal to the obligor, whether in terms of its vesting or its exercise. However the rationale behind such thinking is unclear. In Japan the topic has been the subject of a great deal of debate, with the Supreme Court having ruled against the matter in 2001. Therefore the author shall, in this dissertation, undertake a critical examination of the view that considers the claim of return for secured portions to be subject to subrogative exercise. Cases and theories in Japan will be used to support the above arguments, thereby concluding that as a rule the claim of return for secured portions, being a right which is strictly personal to the obligor in terms of its exercise, cannot be the subject of the obligee's right of subrogation to the obligor, unless there are special circumstances that recognize the forfeiture of nature of the right which is strictly personal to the obligor in terms of its exercise. A brief overview of the central arguments is given below.
The main reason why Civil Law initially recognizes as valid the succeeded person's inter vivos disposition or bequest that infringes on secured portions and thereby, on the one hand respects the freedom of disposition of the succeeded person, and on the other hand allows the right holder of the secured portions to exercise his or her claim of return within the short exercise period in order to recover the secured portions, seems to be due to the following - the fact that our law deems it appropriate for the regulation between the personal relationship and property relationship to be determined by the free will of the right holder of the secured portions who is in a personal relationship. Whether the right holders of the secured portions exercise the claim of return will depend not only on their economic considerations but also on their relationships with the succeeded person as well as other co-successors who will be the counter party of the claim for return. Due to the fact that personal considerations play such an important role, the decision of the right holder of secured portions should not be influenced by his or her creditor.
Therefore even though the right holder of secured portions may be insolvent, intervention through the obligee's right of subrogation to the obligor by the creditors in the personal determination of the right holder of secured portions, would infringe on the latter's freedom of choice, which is also intertwined with his or her personality. This corresponds with the fact that a disclaimer of inheritance cannot be subject to the obligee's right of revocation.
However if there are special circumstances revealing the conclusive intention of the secured portions right holder to assign his or her claim of return, then the subrogative exercise of the claim of return would be possible, given that there is no need to emphasize the personal nature of the right of secured portions in terms of its exercise. However even here it is necessary to determine, based on specific case law, precisely what, including the assignment of the claim of return of secured portions, constitutes an expression of the secured portions right holder's intention.

Ⅳ.
Property possessed by means of succession by the right holder of legally secured portions should be calculated based not on statutory shares in succession but on the right holder’s specific shares in succession. Considering that the purpose of recognizing legally secured portions is to secure the legal minimum of assumed shares, the critical question with regard to the claim of return of legally secured portions can be said to be the actual property gained by the right holder. Therefore, in calculating the property earned by the right holder through succession, it would be appropriate to calculate the property based on specific shares in succession that can actually be earned by the right holder by division of inherited property.
Moreover based on the fact that Civil Law article 1118 applies article 1008 mutatis mutandis, since there is hardly any argument against the view that the special gift received by a coheir should be included in the basic property for legally secured portions without any time limits as provided for in article 1114, it would be in the spirit of article 1118 to base the calculation of the right holder’s property gained through succession on his specific shares in succession, considering the special gift according to article 1008.
Where there is a coheir who received a special gift, calculating the amount of legally secured portions infringed by an ancestor’s bequest or donation has been based, as is the view of this dissertation, on specific shares in succession in lower court cases. However there doesn’t seem to be any such Supreme court decisions. This author hopes and expects the Supreme court to base its decision in the future on the right holder’s specific shares in succession, in line with the purpose of legally secured portions.

Ⅴ.
In the law in force, the lawsuit against return for legally secured portions is one of civil cases under the jurisdiction of the district court. In contrast, the judgment on inheritance division is under the exclusive jurisdiction of the domestic relations court. As the case stands, the two should be settled through separate proceedings. Thus on the construction of the law in force, there is no legal basis to try the demand for return for legally secured portions concurrently with inheritance division. In consequence, coheirs’ co-ownership can be severed only by the lawsuit against the division of public property.
In the aspect of legislation, a general rule deserves establishing in order that a domestic case may be concurrent with a civil case, contingent upon an affiliated case on family litigation act, which is expected to sever co-ownership at once in consideration of the results of return for legally secured portions in the process of inheritance division. However, in practical operation, it is advisable confine the rule to the cases where co-ownership was formed among all coheirs by exercising the rights to demand for return for legally secured portions in the middle of inheritance division including the object of unexecuted donation or unexecuted testation.
The correlation between the return for legally secured portions and inheritance division in coheirs, is closely related to the problem of how the domestic relations court and the civil court will share their roles with regard to the judgment on inheritance division entangled with the lawsuit against the division of public property, as well as how the future of domestic trials will be assumed, not to mention the problem relevant to the legal attribute of property regained by the lawsuit against the return for legally secured portions. Hereafter, it is called on to focus the relevant precedent to be established by the Supreme Court.

Ⅵ.
Finally, this dissertation discusses various issues relating to the exercising period of the claim of return for legally secured portions. Based on assumption that the legal nature of the claim of return for legally secured portions is ‘Gestaltungsrecht’, this dissertation delves into the following.
The legal nature of the exercising period of 1 year as well as 10 years as provided for in Civil Law article 1117 should be viewed as extinctive prescription, based on a ‘good faith interpretation’ of the provision. In general, whether the exercising period of a certain right is extinctive prescription or ‘Ausschlussfrist’(German for the exercising period of ‘Gestaltungsrecht’ stipulated by law) is a legislative policy matter. Therefore ‘Gestaltungsrecht’ does not necessarily mean that its exercising period is ‘Ausschlussfrist’. Moreover, the prevalent view is contradictory in that it considers the 1-year period as extinctive prescription whereas the 10-year period as ‘Ausschlussfrist’, due to its position that the exercising period of ‘Gestaltungsrecht’ is always ‘Ausschlussfrist’.
Civil Law article 1117 is a stipulation of the exercising period of the claim of return for legally secured portions. Therefore, specific rights that arise out of the exercise of the claim of return for legally secured portions, should be examined separately depending on the legal nature of such rights. In other words, as a result of the exercise of the claim of return for legally secured portions, the claim holder acquires the real right-like claim as well as the claim of return for unjust enrichment in respect of the other party's possession, and the real right-like claim would not lapse by completion of extinctive prescription.
On the other hand, in the case where the claim holder of secured portions exercises the claim of compensation in equivalent value against the donee, due to the impossibility of the return of the principal thing, the claim of return for unjust enrichment would lapse by completion of extinctive prescription with passage of 10 years. However even in such a case, the starting point should be not upon inheritance but when the claim of return for unjust enrichment arises as a result of the exercise of the claim of return for legally secured portions.

유류분이란, 피상속인의 의사로부터 법정상속인을 보호하기 위해 피상속인의 재산처분의 자유를 제한하여 법률상 상속인에게 귀속하는 것이 보장된 상속재산 중의 일정비율을 뜻한다. 상속재산 중 상속인 등의 일정한 자에게 유보되는 몫이라고 하여 ‘遺留分’이라고 일컬어진다. 바꿔 말해, 유류분이란 피상속인의 입장에서 보면 상속에 있어서 상속인을 위하여 그의 몫으로 반드시 남겨 두어야 할 일정한 재산을 가리키고, 상속인의 입장에서 보면 법률상 그 취득이 보장되어 있는 피상속인의 재산의 일정액을 지칭한다.
근대사회에서는 계약자유 내지 법률행위자유의 원칙과 소유권절대의 원칙에 근거하여 개인의사에 의한 재산처분의 자유가 인정되고 있으며, 그것이 상속법의 영역에서는 유언의 자유로서 나타나고 있다. G. Radbruch가 표현한 바와 같이, 유언의 자유는 상속법에서 있어서 개인주의적 법원리의 한 표현이자 죽음을 넘어서 연장된 소유권의 자유로서, 근대법에 있어서 유언의 자유는 私的 自治의 한 내용으로서 다루어지고 있는 것이다.
그러나 다른 한편으로 유언자유의 원칙을 무제한적으로 관철할 경우 법정상속인이 모두 상속에서 배제됨으로써 상속인이 경제적으로 궁핍하고 열악한 상황에 처하게 될 위험이 있다. 피상속인의 근친과 배우자에게 상속권을 인정한 이유는 무엇보다도 피상속인 사후에 이들에 대한 부양을 보장하기 위함인데, 피상속인이 재산을 처분한 결과 유족들에게 아무런 재산도 남지 않게 되거나 근소한 재산만이 남게 된다면 이들의 생계는 위협받을 수밖에 없다. 근본적으로 이러한 결과는 유족에 대한 사후부양기능을 전면에 내세우고 있는 법정상속제도의 취지에도 정면으로 반하는 것이다.
그리하여 민법은 유언의 자유를 인정하여 피상속인으로 하여금 자기의 재산을 자기의 의사대로 처분할 수 있는 자유를 인정하면서도, 유언자유의 원칙을 무제한적으로 관철할 경우 발생할 수 있는 여러 가지 폐단을 방지하고자 유류분제도를 규정함으로써 피상속인에 의한 재산처분의 절대적 자유를 제한하고 있다. 이처럼 유언자유의 원칙과 법정상속 간에 존재하는 모순을 해결하고자 도입된 제도가 바로 유류분제도이다. 유류분제도가 유언자유의 원칙과 법정상속제도의 절충안이라고 일컬어지고 있는 것도 이러한 이유에서이다. 다시 말해, 유류분제도는 피상속인에 의한 재산처분의 자유 및 거래의 안전과, 상속인의 생활보장 및 상속재산의 공평한 분배라는 상반되는 요구의 타협ㆍ조정의 산물이다.
그 결과 한국 민법상 유류분제도는 다음과 같은 특성을 가지고 있다. 즉, 피상속인이 자유롭게 처분할 수 있는 재산과 그렇지 않은 재산이 사전에 구분되어 있지 않음은 물론, 자유롭게 처분할 수 있는 재산의 비율이 처음부터 정해져 있지도 않다. 따라서 유류분제도에 의해 생전에 피상속인의 재산처분이 직접적으로 그 시점에서 제약되는 것은 아니며, 상속개시 전 피상속인의 재산처분의 자유는 확고하게 보장된다. 설령 피상속인의 재산처분에 의해 상속개시시 유류분이 침해된다는 점이 명백하더라도, 유류분권을 가지게 되는 추정상속인이 상속개시 전에 이를 저지하거나 유류분을 사전에 보전할 수는 없고, 유류분권리자는 단지 상속개시시를 기준으로 하여 피상속인이 행한 유증이나 증여에 대하여 일정한 한도에서 반환청구권을 행사할 수 있는데 불과하다. 또한 상속이 개시되더라도 유류분을 침해하는 피상속인의 재산처분이 당연히 무효로 되는 것은 아니다. 유류분권리자가 반환청구권을 행사할지 여부는 유류분권리자의 의사에 맡겨져 있으며, 유류분권리자가 반환청구권을 행사하지 않고 일정기간을 경과한다면 반환청구권은 소멸한다.
한국 민법상 유류분제도는 1977년 민법개정에 의해 도입되었지만, 민법은 유류분제도에 관하여 불과 7개 조문밖에 두지 않고 있어 유류분제도의 전체적인 구조파악은 물론 개별적인 법적용에 있어서도 많은 난점을 내포하고 있다. 특히 근래 들어 부동산ㆍ주식 등 자산가치가 폭등한 가운데, 6. 25 전쟁 이후 우리나라 경제 성장을 주도해 온 세대의 자산 대물림 시기가 다가오면서 상속을 둘러싼 분쟁이 크게 늘어나고 있으며, 대법원에 따르면 유류분반환소송도 2002년 69건에서 2008년 295건으로 무려 328%나 늘어났다고 한다.
이러한 배경 하에, 본 논문에서는 현행 민법상 유류분제도의 법적 구조에 관하여 상세히 고찰함으로써, 궁극적으로 유류분제도에 관한 분쟁의 올바른 해결에 이바지할 수 있는 이론적ㆍ실제적으로 적정ㆍ타당한 해석론을 정립하고자 한다.
우리나라에 유류분제도가 도입된 1977년 당시만 하더라도 유류분제도의 도입에 찬동하는 견해가 지배적이었으나, 그로부터 30여년이 지난 오늘날 일각에서는 오히려 유류분제도의 존재이유에 대해 회의적인 시각도 제시되고 있다. 이에 먼저 第2章에서는 유류분제도의 연혁으로서 우리 민법에 유류분제도가 어떠한 경위로 도입되었는지와, 우리 유류분제도의 입법적 계보는 어떠한지 살펴본 후에(第1節), 오늘날의 관점에서도 유류분제도가 여전히 본래의 규범목적을 발휘할 수 있는지, 유류분제도의 기능인 유류분권리자의 생활보장ㆍ가족적 연대ㆍ공동상속인 간 공평유지라는 세 가지 관점에서 살펴보았다(第2節).
第3章에서는 유류분제도의 법적 구조에 관한 해석론에 있어 중추적인 역할을 담당하는 유류분반환청구권의 법적 성질론에 관하여 살펴보았다. 먼저 第1節에서는 논의를 위한 전제로서 종래의 學說과 判例의 태도를 개관하였다. 다음으로 第2節에서는 유류분반환의 방법으로서 종래의 원물반환원칙은 그대로 유지하면서 원물반환이 불가능한 경우의 취급에 관하여도 일반적인 설명이 가능하도록, 방법론적 관점에서 종래의 物權的 形成權說과 債權的 形成權說을 통합적으로 이해하였다. 또한 종래 形成權說의 문제점으로 비판되어 온 내용에 관하여도 形成權說을 옹호하는 입장에서 재검토하였다.
第4章에서는 유류분의 보전에 관한 내용으로서 유류분반환청구권의 행사와 유류분반환의무에 관하여 살펴보았다. 먼저 第1節에서는 유류분반환청구권의 행사 일반에 대하여 개관하였다. 다음으로 第2節에서는 유류분반환청구권의 대위행사를 인정하는 通說을 비판적으로 검토함으로써, 유류분반환청구권을 행사할지 여부는 유류분권리자의 인격과도 밀접한 강한 인적 특성을 가지기 때문에, 채권자가 이러한 유류분권리자의 의사결정에 개입하는 것은 원칙적으로 인정될 수 없다고 새롭게 이해하였다. 그리고 第3節에서는 유류분반환으로서 원물반환의 원칙과 가액반환의 예외에 관하여 살펴보는 한편, 원물반환이 불가능하여 가액반환이 행해지는 경우 그 가액산정의 기준시를 이원적으로 판단한 대법원 2005. 6. 23. 선고 2004다51887 판결에 관하여도 비판적으로 검토하였다.
第5章에서는 실제로 가장 빈번히 행해지는 공동상속인 간의 유류분반환청구에 있어서의 절차법적 쟁점에 관하여 살펴보았다. 먼저 第1節에서는 유류분 침해액 산정시 상속에 의해 취득한 적극재산액은 공동상속인의 법정상속분이 아니라 구체적 상속분을 기준으로 산정해야 한다는 점에 관하여 검토하였다. 다음으로 第2節에서는 상속재산분할심판에서 공동상속인 간의 유류분반환 결과까지 고려하여 상속재산을 분할할 수 있다고 보는 通說에 관하여, 현행법이 유류분반환사건을 소송사항으로, 상속재산분할사건을 심판사항으로 하면서 가사사건에서 민사사건을 병합할 수 있도록 하는 근거규정을 두고 있지 않은 이상, 通說은 이러한 현행법의 해석으로서 법적 근거가 부족하다고 비판적으로 검토하였다.
第6章에서는 유류분반환청구권의 소멸에 관하여 살펴보았다. 먼저 第1節에서는 유류분반환청구권의 소멸을 가져오는 유류분권의 포기에 관하여 검토하였다. 다음으로 第2節에서는 유류분반환청구권의 행사기간에 관한 제문제에 관하여 검토하였다.