Back to the original question. In California this would be considered a Person to Person Transfer (PPT) and there are no laws that would prohibit it. But the system used by FFL's to get state part of the paperwork done has no provision for entering an out of state person info into the system for either the buyer or the seller. So even though it is not against the law the state has effectively prohibited this type of transaction (IE. and out of state seller doing a PPT to a California resident).