>The group was on East 17th Street about halfway down the block when police took a stand and ordered protesters to get on the sidewalk. Before the march, while the group was in Union Square, police handed out flyers and used loudspeakers to warn protesters that they would be arrested if they didn't stay on the sidewalk.
http://7online.com/news/more-than-140-protesters-arrested-in...
Here is the flyer that they were handing out: https://twitter.com/Azi/status/593536703324905473/photo/1
I mean, look at it that other way. People should not be able to openly obstruct traffic. If I were to go run out in the middle of Broadway and block traffic, I would probably be arrested. Just because someone is "protesting" doesn't give them free reign to violate the laws.
This is why public marches/protests require a permit. These guys did not have a permit to do so. See: http://www.nyclu.org/content/know-your-rights-demonstrating-...
> You may be able to march in a public street (as opposed to on a sidewalk) in some circumstances. To march in a street, you must obtain a permit from the Police Department. If you expect to have fewer than 1,000 people in your march, you can apply for a permit at the precinct in which the march will originate. If you expect 1,000 people or more or you prefer to use mail, send your application to: NYPD Investigation Review Section, 300 Gold St., Room 305, Brooklyn 11201. You can download a permit application from the front of the NYPD’s website