Is Barack Obama legally or traditionally prohibited from protesting what Trump does?

I give thanks every day that these ruffians were never president. As long as he keeps it to policy, I don’t see the objection. “I think it is a mistake to invade India because of tweet that hurt feelings in the White House” is perfectly reasonable criticism. “OMG DEATH PANELS!” is not.

The whole premise of the OP is utterly demented: regardless of Obama’s actions and stances after Trump is president, which I’m certain would be limited to urbane pomposity…
Why the hell would matters regarding the pipeline protest change in the least ? It is Obama’s government now harassing the protesters, if the new Trump government continues Obama’s policies, are those policies suddenly wicked because it’s Trump doing what Obama did ? Wouldn’t Obama be a disgusting hypocrite for protesting his own policies ?

And if he wanted the protesters to win, he could arrange that before the transition.

Depending on definitions, I think Grover Cleveland had the most significant career after becoming an ex-president. He was elected President!

Dear God, if my prayers for world peace are unrealistic make this happen instead. And if you have time, try to work Madonna into it somehow.

When Obama described Hilary Clinton as the most qualified candidate ever, he clearly wasn’t remembering the guy who held the job before and probably still had his own set of keys.

Huh? The federal government isn’t harassing anyone at Standing Rock. Crowd/riot control operations are being conducted by the state and local governments and private security. The only federal agency involved is the Army Corps of Engineers, which is responsible for the construction permitting.