stances, the very term "prudential" counsels that it is a proper exercise of the Court's responsibility to take jurisdiction. For these reasons, the prudential and Article III requirements are met here; and, as a consequence, the Court need not decide whether BLAG would have standing to challenge the District Court's ruling and its affirmance in the Court of Appeals on BLAG's own authority.
The Court's conclusion that this petition may be heard on the merits does not imply that no difficulties would ensue if this were a common practice in ordinary cases. The Executive's failure to defend the constitutionality of an Act of Congress based on a constitutional theory not yet established in judicial decisions has created a procedural dilemma. On the one hand, as noted, the Government's agreement with Windsor raises questions about the propriety of entertaining a suit in which it seeks affirmance of an order invalidating a federal law and ordering the United States to pay money. On the other hand, if the Executive's agreement with a plaintiff that a law is unconstitutional is enough to preclude judicial review, then the Supreme Court's primary role in determining the constitutionality of a law that has inflicted real injury on a plaintiff who has brought a justiciable legal claim would become only secondary to the President's. This would undermine the clear dictate of the separation-of-powers principle that "when an Act of Congress is alleged to conflict with the Constitution, '[i]t is emphatically the province and duty of the judicial department to say what the law is.'" Zivotofsky v. Clinton, 566 U.S. ___, ___ (2012) (slip op., at 7) (quoting Marbury v. Madison, 1 Cranch 137, 177 (1803)). Similarly, with respect to the legislative power, when Congress has passed a statute and a President has signed it, it poses grave challenges to the separation of powers for the Executive at a particular moment to be able to nullify Congress' enactment solely on its own initiative and without any determination from the Court.