Precedent.
Definitely precedent. I can’t recall now all the details of the issues presented in the Jones case, but the “Commander in Chief” and Soldiers and Sailors Relief Act argument got thrown out as a defense against POTUS being sued personally, civilly.
The SCOTUS decision is online as are the various arguments presented and issues raised ... now the question is if anyone can actually get far enough along (standing) to get a SCOTUS hearing.