> Would this be the first illegal algorithm?

Not by a longshot. See cryptography before the '90s for the most recognizable example.

All of the very capable models required millions of dollars of compute training on high end low latency hardware.

You can count on your hands the number of high end chip manufacturers and GPU companies, as well as the number of companies with existing high performance clusters. Treat the production and use of datacenter GPUs the same way we treat enriched uranium. We've already started since database GPUs were added to the export control list.