Resignation is often used in these kinds of cases, because there's really no framework to fire them, since they didn't actually violate any of the terms on which they're hired. They should be tried for the crimes they've committed under the jurisdiction of the place where the crime was committed. Not in some random board meeting in a different country.

What happens is that the board says "even if you didn't violate our terms or any local laws, we don't see our organization being able to work with someone like you, so we urge you to do what is best for both parts, which is that you resign voluntarily."

If they don't, then the board can say "the existence of potential criminal cases against you can harm the reputation of our organization, so now you're fired." The outcome is almost the same, but this could create a lot more negative attention to what the company knew about.