United States Supreme Court ruling on DOMA

I find it interesting when I read commentary in the newspapers when people discuss the possibility of the U.S. Supreme Court ruling on DOMA and marriage that each state should be allowed to make their own decision. I find it unthinkable that the UNITED States Supreme Court wouldn't see that it is their responsibility to rule that NO one is discriminated against. It is the UNITED States of America, is it not? The federal government is supposed to act as a check and balance system to stop discrimination and to make sure that everyone is protected. Otherwise, each state would be its own country as in Europe. It is supposed to be "liberty and justice for all" I thought. It shouldn't be that it is okay to discriminate and allow hate in one state and protect a minority in another. It isn't the job of the U.S. Supreme Court to juggle but to act as the beacon of hope and protection for all.