This doesn't just ban A100s. It bans those and "any future NVIDIA integrated circuit achieving both peak performance and chip-to-chip I/O performance equal to or greater than thresholds that are roughly equivalent to the A100." It's a ceiling on the performance that can be exported. In an exponentially scaling industry, this is the equivalent of an announcement in advance of a complete ban on competitive products 2-3…
This is not really new but NVidia was caught by a surprise change in the limits.