In light of the Ukraine story, reupping this:
Trump Says He Would Accept Foreign Government In-Kind Contributions of Opposition Research in the 2020 Elections, in Violation of American Law
In a few pieces in Slate, I explained [corrected] why an offer of free opposition research from a foreign government is a crime, and there is no good First Amendment defense for doing so. (I also have explained that the Steele Dossier involved the payment at market rates from a foreign individual for services, which is legal.) I’m not going to rehash it all here. Click the links for more.