Unpopular Opinion:
Paul Whelan is a shit bag who deserves to be a prisoner in Russia. I believe if you’re in a particular country and you break their laws, you should subject to their justice system. So Paul Whelan can sit in Russia and rot, and Brittney Griner should have done the same.
After a court-martial conviction in January 2008 on multiple counts "related to larceny", he was sentenced to 60 days restriction, reduction to pay grade E-4, and a bad conduct discharge.[9][10] The specific charges against him included "attempted larceny, three specifications of dereliction of duty, making a false official statement, wrongfully using another’s social security number, and ten specifications of making and uttering checks without having sufficient funds in his account for payment."
https://en.wikipedia.org/wiki/Paul_Whelan_(security_director)
They can keep him.