I thought the cover story was that there was a criminal case open whereby Mule needed to send over a sample to prosecute a smuggler or some such.... The truth is out there.
My understanding of this is that there is a treaty by which we are obligated to share samples of fissile materials which are confiscated for tracking purposes. In the subject case, as I recall, a sting was conducted in the nation of Georgia and the Mule was the one who provided a small sample of such.
Again, from memory:
There is a diplomatic cable that informs Russia that Mulehead will be in possession of EU during his travels in and around Ukraine. “Just so you know, Vlad...”
Some have ^speculated^ that he was going to take a side trip to Russia. No confirmation on whether he did or did not.