Apparently even Henry Louis Gates Jr. isn't immune to being arrested for "contempt of cop." Discretionary arrests for minor charges happen all the time. It's only rare when it happens to somebody of Professor Gates' stature and becomes national news.
If you're a police officer and run into the director of Harvard's W.E.B. Du Bois Institute for African and African American Research - even if he is rude to you - best to let it slide. Really.
In my book Cop in the Hood, I described how officers can invite a person outside in order to arrest him for disorderly conduct. I gave the hypothetical of a domestic dispute: "Though the officer believes this argument will continue and perhaps turn violent, there is no cause for arrest. Police may not order a person from his or her home. But an officer can request to talk to the man outside his house. At this point the officer might say, 'If you don't take a walk, I'm going to lock you up.' The man, though within his rights to quietly reenter his house and say goodnight to the police, is more likely to obey the officer's request or engage the police in a loud and drunken late-night debate. ... If a crowd gathers or lights in neighboring buildings turn on, he may be arrested for disorderly conduct."
