> With a normal NDA, if you publish information you're not supposed to, they can go to court and prove that the information was covered by the NDA and then get an order to stop you from continuing to publish it or sue you for damages.
That is exactly what happened in this instance. The court determined he did violate the agreement. The information did not need to be classified, any "mention of intelligence data or activities" was covered. The agreement outlined the damages that would be assessed -- the proceeds from the publication.
https://cdn.arstechnica.net/wp-content/uploads/2019/12/snowd...
Son of Sam laws and prior restraint is probably not relevant here, these obligations are the result of a voluntary contract he signed. All of the case law I'm aware of surrounding those are about obligatory restrictions, not ones that were voluntarily accepted. In general, prior restraint has national security exceptions, and there's no way any sane court is going to rule that the NSA secrecy agreements aren't legal.