How is the 1973 war powers act a check on presidential power? (think of seperation of powers)

The War Powers Resolution (also known as the War Powers Resolution of 1973 or the War Powers Act) (50 U.S.C. 1541–1548)[1] is a federal law intended to check the president's power to commit the United States to an armed conflict without the consent of the U.S. Congress. The Resolution was adopted in the form of a United States Congress joint resolution. It provides that the U.S. President can send U.S. Armed Forces into action abroad only by declaration of war by Congress, "statutory authorization," or in case of "a national emergency created by attack upon the United States, its territories or possessions, or its armed forces