As a general note to our European friends, questions on how laws work in the United States are heavily dependent on exactly where the action is taking place. The exact same thing might be legal, illegal, enforced or not enforced depending on
A) exactly where it takes place
B) which law enforcement agency is involved (county sheriff, town or city police, state police, Federal Bureau of Investigation (FBI), the federal Alcohol Tobacco and Firearms (ATF) people, customs and border patrol, immigration and naturalization, port authority, campus police--We have more police agencies than you can shake a stick at.)
C) who is involved and what the circumstances are
So to get a good, accurate answer about what happens in the USA from a law enforcement perspective, and even whether a particular action is illegal, we need to know a lot of detail about who is involved, precisely where the incident happens, and what the incident is.
We're big. The medium-sized state of Oregon, where I grew up, is larger than the whole of the isle of Britain. It can take more than 8 hours, on our 65 miles per hour freeways, to drive from Sacramento in the middle of California to San Diego in Southern California.
We're split into distinct states with their own legislatures and social mores. It's confusing enough for us, let alone for us to answer your questions. Heck, even we have to ask each other about how something would work in another state.
Personally, I love sharing US culture with writers from abroad. Bring it on! But that's why we ask so many detailed questions, so we can provide hopefully accurate answers. Otherwise it's a big, frustrating, "it depends".