It's your constitutional right to assemble. If you get a million people, for example, assembling, you cannot keep the same rules of traffic as usual. (It would be impossible (and the attempt dangerous) to try to keep a million people on the sidewalk.) [Edit: In other words, your constitutional right to turn out and assemble is independent of whether there will be enough space for you on the sidewalk.]
As for the Wall Street bankers, who do you want to prosecute for what?
Those that committed it, for fraud. It's an open-and-shut case if the power existed to prosecute it.