Is there any SCOTUS precedent for this? It seems like a huge 1A issue for the government to limit self hosted access to a foreign country’s LLM.

After what happened to TikTok, I don't think it's a stretch.

TikTok wasn’t open source and able to be run on your own hardware. Banning Alibaba’s models (or even a personal fork of them) running on your machines seems hard to defend in court.