I'll just let Chief Justice Charles Evans Hughes explain it to you...
"EQUAL JUSTICE UNDER LAW"-These words, written above the main entrance to the Supreme Court Building, express the ultimate responsibility of the Supreme Court of the United States. The Court is the highest tribunal in the Nation for all cases and controversies arising under the Constitution or the laws of the United States. As the final arbiter of the law, the Court is charged with ensuring the American people the promise of equal justice under law and, thereby, also functions as guardian and interpreter of the Constitution.
The Supreme Court is "distinctly American in concept and function," as Chief Justice Charles Evans Hughes observed. Few other courts in the world have the same authority of constitutional interpretation and none have exercised it for as long or with as much influence.
And Madison had written that constitutional interpretation must be left to the reasoned judgment of independent judges, rather than to the tumult and conflict of the political process. If every constitutional question were to be decided by public political bargaining, Madison argued, the Constitution would be reduced to a battleground of competing factions, political passion and partisan spirit.
In retrospect, it is evident that constitutional interpretation and application were made necessary by the very nature of the Constitution. The Founding Fathers had wisely worded that document in rather general terms leaving it open to future elaboration to meet changing conditions.
link...
I don't know... perhaps you know more than he does.