The amount of money and strategic (national security) interest involved in AI seems to be at least a few orders of magnitude above scientific journal publication fees and the music industry combined.

How will they physically enforce the ban. They would have to go into everyone's house to search them. Using an llm also doesn't give off any signatures like BitTorrent or even visiting a papers site might. Can you propose even one method of enforcing it (I cannot)

Practically, they could enforce this in similar ways they enforce CSAM restrictions. Dialing back the severity, restrictions on any cloud hosting provider from serving these models is probably going to cut usage down tremendously.