So if he had allowed only American students to work on the project it would have been ok ?
If he had offered a seminar for American students only, they would propably have gotten him for racism LOL.
The scientific community and military interests usually don't go along well for several reasons... but i see this pretty much as a direct consequence of allowing foreign students to study at american universities in the first place. I.e. it, or something like it, was bound to happen.... propably already happened dozens of times, just this guy happened to get caught. Banning foreign students from US universities however would rightfully cause a public outcry of epic proportions, so instead this guy has to take the fall. It's actually quite hypocritical in my eyes really. Like the government being frustrated about what they know will happen anyways.
Like freely placing a giant delicious cookie jar of still warm cookies under the noses of foreign powers and then punishing your own citizens if someone who wasn't "supposed to" actually ate a cookie.
Course there is no easy answer, but this isn't a solution (there isn't really one if you want to keep living in a "free" country

) ... this is the military/government venting frustration in my eyes lol.
This professor simply treated foreign students just like any other student. If foreign students are supposed to be "2nd class students with restricted access" then frankly ... someone from the government needs to inform the public about it and deal with the consequences lol. And if military secrets are supposed to be kept then the military needs to use its own labs and its own people. Period. No way around it. Intereferring with the scientific community and the work they do and how they do it certainly will only end in frustration for BOTH sides and either end up with professors being in jail or the scientific process being stymied by military interests.
As i said... in my eyes, assuming the actual facts match somewhat up as presented: Hypocrisy as elaborate as it gets. Are universities an extension of the military now ? Do students need security clearance before signing up for seminars ? No ? Well how can you arbitrarily put this guy in jail then, while all kinds of secrets are leaking out of all kinds of fields (including business processes, manufacturing processes, chemistry and material knowledge et cetera.) to foreign countries on a daily basis ? That is pretty much a fact. It's called an international scientific community and the US pretty much benefits from it as much as everyone else. Did someone forget the tell the military?

Seriously... if you want to keep a secret... then for christs sake use secure facilities with your own staff and don't blame professors for doing their job lol.