If our reading of the US Constitution is correct, you're allowed to drive your car as fast as you want, wherever you want. Regrettably, many municipalities have not acknowledged this inalienable right, and they have found that infringing upon it can provide a steady stream of revenue.
Actually, you may not be totally secure. Last month, Computerword reported that hackers have broken into Trapster's database. The company emailed all of its members notifying them that "it's best to assume that your e-mail address and password were included among the compromised data." You know, there really ought to be a law against that sort of thing.