To prohibit the conduct of a first-use nuclear strike absent a declaration of war by Congress.

Restricting First Use of Nuclear Weapons Act of 2017 This bill prohibits the President from using the Armed Forces to conduct a first-use nuclear strike unless such strike is conducted pursuant to a congressional declaration of war expressly authorizing such strike. "First-use nuclear strike" means a nuclear weapons attack against an enemy that is conducted without the President determining that the enemy has first launched a nuclear strike against the United States or a U.S. ally.