Well I guess the more interesting question is why the Supreme Court's opinion prevails over the opinions of the other two branches of government which are, in theory, co-equal.
The question is illustrated best by the relatively recent case where the Massachusetts Supreme Court overturned the marriage law in Mass, and "interpreted" it to require the Commonwealth to recognize homosexual marriages. Thus, they completely took the issue out of the hands of both the legislature and the Governer, since to overturn their decision would have taken a couple years (for a Massachusetts Constitutional Amendment), during which time the Commonwealth would be forced to perform gay marriages to anyone applying.
The Governor (one Mitt Romney) SHOULD have shown some spunk and rebelled against this judicial power grab. As a practical matter, he could simply have declared that no executive branch employee could issue a marriage license to a homosexual couple (on penalty of termination). Politically, the case would be that this is a question that is eminently one for the policy makers in the Legislature, and not the Court.
On a related note, both executive branch and legislative branch elected officials swear an oath of office in which they swear to uphold the constitution of the state and the U.S. Thus, they are OBLIGED to act in office according to the Constitution as they understand it. WHY DID NOT A SINGLE DEMOCRAT VOTE AGAINST ACA DUE TO ITS RANK UNCONSTITUTIONALITY?
Clearly, they consider their oath of office to be a meaningless gesture, with no substantive obligations attached.
