Abstract This paper asks under what conditions a transitional administration mechanism, installed from the outside into a territory that has lost its capacity to act, can claim legitimacy under international law. Specifically, it dissects the legal structure of the "Board of Peace (BoP)" established in Gaza by UN Security Council Resolution 2803 in November 2025, and assesses its legitimacy. In its demonstration, this paper adopts two independent theoretical paths. The first is a "typology of malignant governance" extracted from an inductive comparison of major historical transitional administrations (Namibia, UNTAC, Iraq/Afghanistan, Kosovo). The second is a deductive foundation of the jurisprudence that strictly distinguishes between legal capacity (capacity to hold rights) and the capacity to act, explored through the comparative private law of France, Germany, Japan, and the United States. These two paths are integrated and formulated as the "Seven Requirements for Legitimate Transitional Administration": (1) Explicit preservation of legal capacity, (2) Explicit statement of objective termination conditions, (3) Inclusion of procedures to confirm the will of the residents, (4) Restriction of conflicts of interest, (5) Preservation of governance calories, (6) Construction of social self-immune functions, and (7) Design of pressure valves. Evaluated against these criteria, it is proven that the BoP is a "crystallization of illegality" harboring fundamental flaws across all requirements due to its design philosophy of "exclusion and control," thereby constituting an unprecedented "privatized transitional sovereign authority". Finally, this paper presents a concrete architecture (hybrid DDR, bypass funding, elder inclusion, and the introduction of pressure valves) to transform this illegal structure and truly restore the capacity to act of the Palestinian people. It concludes that a transitional administration mechanism can only justify itself as a time-limited "incubator" for the governed people to regain their capacity to act through a final free election, and that presenting the conditions for its recording and transformation is the very mission of international legal studies.