While the Constitution vests residuary powers with the Union (Centre), the ultimate authority to determine if a subject falls under residuary powers rests with the Parliament. This is derived from the interpretation of Article 248 of the Constitution, which states that Parliament has the power to make laws with respect to any matter not enumerated in the Union List or the State List. In case of dispute or ambiguity, the courts, particularly the Supreme Court, may have the final say in interpreting the Constitution, but the initial and legislative power to address residuary matters lies with the Parliament.