Thanks to US we already know how to handle this - there is a plenty of secret locations in various different countries where the perpetrators can be safely tried and then handled according to the sentence.
I doubt the US would take their citizens suddenly disappearing in a country very well either, and keeping it hidden would be difficult. Maybe you could secretly convict a soldier who desecrated corpses or something, but people like Gina Haspel would be nearly impossible without ramifications.