Vladimir Putin: Mueller can use this [extradition] treaty to make an official request to us… in this case this kind of effort should be a reciprocal one… For instance we can bring up Mr. Browder… They sent a huge amount of money $400,000,000 to Hillary Clinton!
I don't know if the money was legally contributed (in America), but it was illegally obtined (in Russia).
[With thanks to Pablo Mayhew for putting this in a comment.]