Educating the Police
Just as there are bad politicians, there are bad policemen. These are the guys who play it safe with a default answer of "It's not allowed" when they really don't know the law. If you ask for proof of such laws on the books, you may find yourself with a one-way ride to the police station.
There are so many laws and regulations on the books these days (some obsolete) that it's hardly to be expected that the police know each and every one of them. Although it's their job to know, often City Hall will back them up when a minor infraction of booting a busker off their pitch occurs.
The police have usually been called to your pitch for a reason. You've probably allowed your crowd to block access to businesses, created noise complaints, or someone has taken issue and perceived you to be loitering or begging. The police will tell you why they are there and will issue a warning or summons.
To counter this scenario, it's probably a good idea to investigate all this first before performing. You can avoid these pitfalls and know what the laws really are pertaining to busking. A little research can go a long way.
By busking a city whose policemen are not totally familiar with the local laws, you may find yourself being harassed by Officer Friendly's default answer. Fortunately, there are a few things you can do to prepare for the inevitable.
First, never be rude or try to show up the police. They are the keepers of peace in society and they are only doing what they think is right. Without them, there would be utter chaos. It's up to you to educate without offending which can be a daunting task. For Heaven's sake, don't quote the First Amendment! This is akin to arguing.
Secondly, you've done your homework and have researched the law. You've found busking to be perfectly legal supporting your position. You've taken the time to copy the laws and make a little artistic pamphlet high-lighting them in a clear and concise manner.
Thirdly, you've stopped your show and politely handed the policeman your pamphlet mentioning -
"Well officer, as a law abiding person myself, I was also concerned about this. So, rather than go out and break the law, I first checked with City Hall. They were very clear about street performing."
You've shown him the actual laws all the while being factual, informative, displaying an even disposition, and behaving in a non-threatening way. This is actually the hardest part when, in fact, you want to strangle him for ruining your show. Your acting should be worthy of an Oscar!
Fourthly, don't gloat when you've proven yourself right and the officer wrong. In fact, you do the opposite. You tell the officer that you appreciate the concern over safety issues and will make sure nobody is blocking the sidewalk, too loud, etc. You're showing respect to the policeman and the community.
Fifth, you may want to hand several pamphlets to him so he can distribute them among is fellow officers. This actually goes a long way in preventing the same occurrence with other officers happening the very next night.
By following these simple guidelines, you can probably make friends with the officers (!) and avoid further incidents. By gently educating the local police, you are also helping your fellow street performers in the area who can also be given the pamphlet to reproduce and redistribute.
See you in jail!