Regardless of what various shoe-lickers or rat caretakers will tell you, photographing anything that is in public view—including federal buildings and the police—is 100% legal. We were reminded of this by watching this video from photographer Javier Soriano, who was in the 103rd Street subway station in Harlem videotaping officers detaining a man. Two bystanders accost Soriano for filming, and one smacks his camera out of his hand, threatening to beat him if he continues to film.

Soriano writes:

Friday, October 19th, 2012. New York City - I was at the train station on 103 St in Harlem. I saw a NYPD officer searching a young black man. I started filming them. A Latino man said I was retarded for filming them. A Black man said was illegal for me to film them. One of the officers told him something against me, then the Black man came to me and smacked my camera and as a result, my camera is not working properly now.

Indeed, when the first man yells at the police, asking them why they didn't tell Soriano to stop, one replies, "Because that's against the law!" If there is any doubt that filming police interactions in public is legal, the NYPD has incorporated two bystanders filming officers with cellphone cameras into their stop-and-frisk training.

NYPD Stop & Frisk Demo 1 from Gothamist on Vimeo.

[UPDATE]A commenter rightly points out that you may film anything in public so long as you are not interfering with legitimate law enforcement activity. This stipulation is sometimes inconsistently applied by law enforcement.