When President-elect Donald Trump takes office, he'll inherit U.S. military interventions in seven countries — Afghanistan, Iraq, Libya, Pakistan, Somalia, Syria, and Yemen — and little in the way of congressional restraint on his own war-making powers. That's because all these wars are implausibly placed under the same legal cover of the 2001 Authorization for Use of Military Force (AUMF), the document authorizing military action against the terrorists responsible for the September 11th attacks.
For the rest of tenure of Presidents George W. Bush and Barack Obama, Congress has failed to exercise its constitutional authority to initiate and limit the president's war-making, even as U.S. foreign policy attention focused on nations and terrorist groups with little or no connection to 9/11. Soon, as Politico explains, that lax precedent will apply to Trump:
“You could easily see him wanting to ramp up the war on terror and take it to new parts of the globe,” said Rep. Adam Schiff of California, the top Democrat on the House Intelligence Committee. “There are few limits on what he can do.”
Democrats like Schiff worry that without an updated legal framework to govern the war on terror, [...] Trump is likely to have almost unlimited powers as he takes over U.S. military involvement in Iraq, Syria and Afghanistan and potentially ratchets up ongoing efforts to hunt down and kill suspected terrorists the world over. [Politico]
Though some congressional Democrats may attempt to pass a last-minute AUMF that would limit Trump's policy options, it is not expected to succeed. However, Trump himself may seek an updated AUMF next year. "It wouldn't bother me at all doing that," he said of passing a new resolution in an interview with Bill O'Reilly this past spring. "We probably should have done that in the first place."