No official court challenge yet, mostly lawyers/academics putting out papers after California's SB 1047. The general argument I've seen is that because weights are generated during training, and not written line by line by humans (like source code), it's non-expressive and no human understands what the raw weights mean, therefore no human reads them as expression.

There's also Texas v. Johnson (the flag burning case), the court rules that for something to be protected speech it must contain an intent to convey a specific message, and a great likelihood the message will be understood.

The core decision, if ever tested in court, will come down to "Are model weights an expression of human ideas? Or are they purely a mechanical tool?"