Yep different in every state. California it's really easy to register them, of course getting a motor shipped can a problem. Here it's registered, M2 license, dot helmet, horn, head light/tail light, grey area is mirror, brake light and turn signals "CHP requires them". So I assume you need the last three to drive on highways, seeing they aren't allowed on freeways and it's the only other place the chp patrols. DMV says mostly the same thing but they kind of contradict themselves, by saying you can't drive on a highway after telling you what you would need to drive on the highway.
I have everything on mine and wear a DOT helmet. I think the more street legal you make it, the less likely you'll get sited if a cop pulls you over.