[Publius6961]

Because they can take up his constitutional eligibility case,rule him a fraud and then send him to the gallows.

Granted, all crimes against humanity do not involve death camps, mass starvation and jungle wholesale massacres, so that hyperbole is understandable but a bit extreme.
But lacking that option, I could be persuaded to support the original suggestion.

[DarthVader]

They can send him to prison forever.