There should be a way for the people to veto a law in a referendum, like in Switzerland. That way politicians would be more cautious passing laws which they know that the public probably won't like and probably will veto.

The current US system only provides "checks and balances" between political parties, so when one party cracks up (meaning, gets bought by special interests and turns against the people) we only can pray that the other party will come to the rescue. But when both parties agree and team up against the people, i.e. when there is a political market failure like in the case of SOPA (or ACTA), theres no way for the voters to defend themselves.

It is not another law that is needed, but a general possibility to override unpopular laws.