Technically the US government is allowing Anthropic to serve the models to any US citizen, and it's Anthropic who decided that's impossible to comply with and so they pulled the model for everyone. I guess a US business with non-citizen employees could work.
A lawsuit would be a hard sell though, because Anthropic themselves argued that the technology is dangerous. Even if many people on HN might think that Anthropic was scaremongering about Mythos, a court is probably going to take their assessment at face value, and courts are loathe to find against governments in cases of national security.
There's also the issue that these models are getting better through an iterative process, so even if the line between GPT 5.5 and Fable/GPT 5.6 is somewhat arbitrary, it doesn't mean that the government shouldn't be able to draw a line at all. So you're left arguing that they drew the line too early, which is subjective.
A lawsuit would be a hard sell though, because Anthropic themselves argued that the technology is dangerous. Even if many people on HN might think that Anthropic was scaremongering about Mythos, a court is probably going to take their assessment at face value, and courts are loathe to find against governments in cases of national security.
There's also the issue that these models are getting better through an iterative process, so even if the line between GPT 5.5 and Fable/GPT 5.6 is somewhat arbitrary, it doesn't mean that the government shouldn't be able to draw a line at all. So you're left arguing that they drew the line too early, which is subjective.