No, when the power to define is given to Congress, it is not the business of the Supreme Court to take that power into it's hands. Justice Brennan has already tried that gambit. Congress can, should, must, take that power back.
John / Billybob
Well, it looks like the 14th doesn't give the congress the power to define, but to enforce.
The Supreme Court apparently has the power to interpret the U.S. Constitution and to determine the constitutionality of laws passed by congress and the state legislatures. (ruled so in 1803)