In recent months, no less than 18 states have introduced – and, in some cases, actually voted on – legislation designed to curb mass protests, citing demonstrations at oil pipeline sites, airports and other public places. Supporters of such legislation, some of which is inspired by ALEC, the American Legislative Exchange Council, say it's designed to protect public safety. Others say these proposals would have a chilling effect on the right to protest. Don Kettl, a senior fellow at The Brookings Institution, says the First Amendment could not possibly be more clear on this.

"Any effort in history, in the American republic, to try and restrain that has always been rejected. It's just hard for me to imagine there's any possible constitutional basis on which restrictions could be put on the ability of the people to gather, to talk among themselves, to demonstrate as they like, even in large numbers."

None of the proposed legislation actually has been passed into law, and some states have shelved legislative proposals of this sort. But Kettl says it's a moot point because such legislation would never pass constitutional muster.