U.S. officials familiar with the planning said options for "reclaiming" the vital waterway include close cooperation with Panama's military and, absent that, possible war.
Not that I have any faith in the R congress to have a spine, but I'm not seeing how he even could do so if he wanted to without consent of Congress. Pretty well all the direct actions taken in the last couple decades come from the AUMF but that's at least theoretically supposed to be linked to terrorist activities.
Supposedly he'd have to have a reason, such as terrorism like you say, in order to pull a Bush Jr Invasion.
In todays wacked out evil af world... who knows. Im wondering why he's just not using the CIA to "covertly" do this. But then again it could all be a bluff.
Apparently part of the treaty that returned the canal to Panama means that either Panama or the US can unilaterally ensure the canal's neutrality if they feel it is threatened. So I'm sure they could make the argument that it falls under this. It would be bullshit, of course, but so are all of their other arguments.