The offense in law 12 is USB. The list under that is a non-exclusive list of example of unsporting behavior. I don’t think it is outside the Laws for a referee to consider it unsporting in some contexts beyond SPA, but I don’t think the Laws expect it to be a caution unless there is something more than merely getting in the way. I’d like to see IFAB give more clarity in this space. On the one hand, I think GKs should just be left alone. But I watch professional games, and opponents always get in the way of the GK any time there is the remotest possibility of a counter attack, and it is never called. Of course, if it is called, the opponent wins, as instead of the GK getting to throw/punt the ball quickly, it becomes an IFK, which gives the team more time to get back. That’s part of why I would like to see it considered USB, as the IFK sanction really isn’t a sanction at all. But if IFAB is happy with people running in front of GKs who try to distribute the ball, I’d like to have them add something to the guidance about when an attacker crosses the line into an offense beyond sticking a foot in to challenge the actual kick. (Back when USSF published Advice to Referees, they formally taught that interfering with the GK was a form of USB, and had other additional examples. That formal teaching is no longer out there as far as I know.)