Does this fall into treaty territory or some loophole that doesn’t require congressional approval
Presidents can sign treatys, they need 2/3rds approval from the Senate to be ratified. There are lots of treaties the US is signatory to but can't get ratified like Nuclear Test Ban Treaty, Paris, Banning Landmines. But the President has pretty wide powers to withdraw from treaties. George W. Bush got lots of criticism for withdrawing from the ABM to try and build a missile defense system, but I am pretty sure he was able to do it without congressional approval and the ABM was ratified.