How could the U.S. military be used for Trump's mass deportation plan?

President-elect Donald Trump has vowed to start the largest deportation effort in American history — his signature 2024 campaign promise — as soon as he takes office, signaling this week that he would enlist the help of the U.S. military for the massive operation to deport undocumented immigrants.

Earlier this week, he shared a social media post indicating that he'd declare a national emergency and deploy military assets to carry out deportations. 

Still, how exactly the military would be tapped to carry out this promise of mass deportations is unclear. And there are untested legal questions about involving service members in immigration enforcement operations.