There are two kinds of personal vis sources, one is external to the body, and the other is internal to the body. In the Normandy Tribunal the external ones are problematic. They need to be registered with the Tribunal. And, if located close enough to the covenant, they become seisin. If they are far enough away from the covenant, they become legacies.
Alexei used some of his build points coming to Mons Electi to create a personal vis source, as it were. His vis source he reasoned comes from being a Milite, and providing services, a small measure of compensation. I call it a protection racket 
The point being, his vis is held on account with House Mercere. He doesn't touch it, until such time as he needs it, and then he can have a redcap deliver it. This is kind of skirting the Peripheral Code in the Normandy Tribunal, but they don't know about it, and Mercere is all about confidentiality of account holders.
I would like to reconcile the personal vis source in this case is to change it up a bit, and tie it to your desire to conduct reseach into longevity rituals which don't cause sterility. Jormungand 'svis source could be his seed, it could've been caused by the same ritual. Making the vis source of his body prevents a covenant, or anyone else being able to exercise ownership of the vis. Additionally, because the vis source is his seed, Jormungand is not infertile. So he knows that is possible to do this, he just isn't sure how it can be done, and hasn't done any investigation, other than noting that some of the rituals he has performed previously have caused sterility in other people. It also leaves open the possibility that it could be impossible, and is a fluke for people who's seed is also vis.
Discuss in the table talk thread, I've posted a link there. I'll edit this last paragraph out after we've discussed.