The police have done it for decades - investigating protestors is nothing new - I'd say what the military does with the information once it has it is what is important.

Protests are always going to be filmed by law enforcement, it's a very common practice. If that information is later used for harrassment purposes, or something of that sort then certainly the military has gone too far.

But I don't think there are any laws that prohibit the military from monitoring and recording public protests... The article is very vague about the "spying" that occurs, so I'm not really sure if it's much of anything beyond standard practices at protests.