Democracy does not stop politicians from doing what they want and an apathetic voting public is the best enabler a politician could ask for. The law does not stop many politicians from doing what they want as they are able to work around it, find loop holes, or just break it without repercussions because of their connections.
The whole reason they are trying to shut down the government right now with Obamacare, has to do with Obamacare making big businesses pay more for their employees health care, even though everyone in lower or middle class are actually paying less than they do now.
The big business holds the politicians by their balls and can twist them one way or the other with the power of money. Politicians seem to be able to do whatever they want, because they are backed up by money.