Israel has justified the construction of its barrier wall as a nonforcible measure taken in selfdefense to protect its citizens against terrorist attacks emanating from the occupied Palestinian territory. This essay addresses two issues. First, was the International Court of Justice’s conclusion in paragraph 139 of the advisory opinion Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory that “Article 51 of the Charter has no relevance in this case” wellfounded? This question involves consideration of three interrelated substantive aspects of paragraph 139: the Court’s finding that Article 51 was irrelevant because Israel did not claim that the attacks against it were imputable to a foreign state; the relevance of the Court’s reliance on the fact that Israel exercises control over the occupied Palestinian territory; and the Court’s conclusion that the situation differs from the circumstances contemplated in Security Council Resolutions 1368 (2001) and 1373 (2001) and that, accordingly, Israel could not invoke these resolutions in support of its claim to be exercising a right of self-defense. The second issue is whether the approach of the Court to the substantive content of Article 51 can be defended as an appropriate discharge of its judicial function. To avoid undue suspense, let it be said at the outset that paragraph 139 is well-founded, and the Court properly fulfilled its task.