> The LLM ban is unenforceable

Just require that the CLA/Certificate of Origin statement be printed out, signed, and mailed with an envelope and stamp, where besides attesting that they appropriately license their contributions ((A)GPL, BSD, MIT, or whatever) and have the authority to do so, that they also attest that they haven't used any LLMs for their contributions. This will strongly deter direct LLM usage. Indirect usage, where people whip up LLM-generated PoCs that they then rewrite, will still probably go on, and go on without detection, but that's less objectionable morally (and legally) than trying to directly commit LLM code.

As an aside, I've noticed a huge drop off in license literacy amongst developers, as well as respect for the license choices of other developers/projects. I can't tell if LLMs caused this, but there's a noticeable difference from the way things were 10 years ago.