So, Congress is arguing that he is violating the constitution even though Congress gave blanket authority to the POTUS to decide what wars are necessary after 9/11?
And the US military has been committed to NATO since 1949. Several times the US military has been to war under the request of NATO, with no input from Congress.
Following the attacks of Sept. 11, 2001, Congress handed President George W. Bush blanket authority to make war, and the battlefield has since been classified as anywhere in the world, even on U.S. soil. Both the Afghan and Iraq wars were launched under this authority, and President Obama continues to claim the same executive power to carry on theaters of conflict in other regions.
Similarly, Congress committed the U.S. to the North Atlantic Treaty Organization (NATO) in 1949. Following the 9/11 attacks, troops were deployed under NATO authority following a United Nations resolution which declared the late Iraqi leader Saddam Hussein to be in breach of the U.N.’s terms. Congress did not specifically authorize those invasions, but Republicans were adamantly supportive of the president.
So.....it looks like Congress needs to make up their minds. You can't pass a law giving the office of the President the power to declare war (War Powers Act post 9/11) and then try to pass a law saying that it is an impeachment offense to declare war