自從十九世紀以來，隨著國家政治力量和市場經濟活動的快速擴張，臺灣原住民對於土地和自然資源的傳統主權也面臨更多的挑戰；如今，許多原住民部落試圖在傳統與現代的制度之間尋求平衡點。本篇論文旨在討論原住民地權流失的邏輯，並對兩個透過社區合作、管理共用資源、創造集體利益的泰雅族部落，進行案例分析。本文透過新制度經濟學的觀點，討論內在制度對社區凝聚力的影響作用，以及gaga (一種泰雅族的傳統制度) 內涵的演變。經由案例分析，本文認為，儘管作為正式組織的gaga已經不復存在，但是gaga作為規範與共同約定的意義仍然影響著案例中人們的制度選擇。最後，本文建議，現有的地權制度應可進行調整，使其符合經過原住民部落傳統內在制度所演化出來的共用資源自主治理模式，如此一來，更可以降低許多因為國家政治與市場經濟互動下產生的衝突與矛盾。

The sovereignties of land ownership and natural resources of Taiwan’s indigenous peoples have been seriously challenged by the expansion of state power and the workings of the capitalistic market economy since the 19th century. Many indigenous communities have attempted to adjust to and negotiate with modern institutions. This article analyses the logic of the loss of indigenes’ land tenure and examines two communities of the Atayal tribe that seek to self-govern and manage their common-pool resources (CPR) through collective action for collective interest. Furthermore, drawing from neo-institutional economic perspectives, this article discusses how traditional institutions affect the solidarity of communities, focusing on how the Atayal’s traditional institution of gaga has changed over time. Despite the fact that the formal organization of gaga no longer exists, its commonly accepted codes of conduct continue to regulate behavior and affect institutional choice. This article suggests that the existing land tenure system should be reformed to better match the model of self-governing common-pool resources in the indigenous areas where traditional institutions have gone through internal transformation. Such a reform would diminish the conflicts emerging from the interaction between state power and the capitalistic market economy.