This excerpt is a direct quote from Slate.com

The basic rule of American constitutionalism is this: Before the government can forbid you from doing anything, it has to provide a reason. “Because we say so” does not count as a reason. To limit ordinary liberties (like selling eyeglasses), most any reason is good enough. To restrict fundamental liberties (like using birth control while having sex), however, the government must have a really important reason. (Getting to decide which liberties are “fundamental” is one of the cooler parts of being a justice.) Under the equal protection clause, even if the government has a plausible reason for putting a burden on you, it also has to explain why it treats other people better. If the justices suspect that the government may simply dislike people like you, they will demand an especially convincing explanation for the different treatment. And if the government wants to interfere with your liberty by actually taking your house or property, it has to pay you “just compensation”; and even if it’s ready to fork over compensation, the town can’t take your stuff at all unless it’s going to use it for a “public purpose.” (Current hot topic: Is forcibly taking old people’s homes to make way for a spiffy new Wal-Mart really a “public” purpose?)