Absent a special statute of limitations, the general federal statute for noncapital crimes is five years. So Joe was in the clear long ago on that particular Ukraine piece of the family influence peddling business
https://www.thefederalcriminalattorneys.com/federal-statute-of-limitations
Oh, but New York taught us something. We don't have to pay attention to mere statutes of limitations. No! We can simply create a new retroactive law to restore culpability after a statute of limitations has expired.
As long as we are in make-stuff-up lawfare land, a prosecutor with no scruples in front of a judge with none might argue successfully that the statute was tolled while the defendant controlled the justice department.