In a big victory for Texas' Republican Attorney General, the Supreme Court today threw out interim congressional redistricting maps drawn by a federal court in Texas that had favored Democrats.

In a unanimous and unsigned opinion the Supreme Court said that it was "unclear" whether the Texas court had followed the appropriate standards in drawing interim maps to be used for the 2012 election and it ordered the lower court to go back to the drawing board consistent with new guidance from the Supreme Court.

The dispute over the congressional maps has wreaked havoc in Texas and already caused the state to push back its primary date from March to April. How the maps are drawn determines which neighborhoods and areas are represented in which congressional district and influence which party gets more seats in congress.

At issue are two very different set of congressional redistricting maps drawn after 2010 census numbers awarded the state four new seats in the U.S. House of Representatives. Minorities account for the majority of the growth.

One set of maps was drawn up by the Republican dominated State legislature. Democrats and minority rights groups immediately criticized the maps arguing they didn't reflect the growth of minority representation.

Because Texas is a state with a history of discrimination in voting, it is subject to a provision in the Voting Rights Acts that requires the state to get approval or "preclearance" from the Department of Justice or a federal court in Washington before the maps can be implemented.

While the preclearance process plays out in a federal court in Washington DC, a Texas court drew up another set of maps to be used on an interim basis for the next election.

Those court-drawn maps triggered today's decision.  Texas Attorney General Gregg Abbott charged they were improperly drawn up and should have paid at least some deference to the maps drawn up by the state legislature.

Today the Supreme Court agreed, writing that the Texas court should have used the legislature drawn maps at least as a "starting point".

The court said the legislature drawn maps "provides important guidance that helps ensure that the district court appropriately confines itself to drawing interim maps that comply with the Constitution and the Voting Rights Act, without displacing legitimate state policy judgments with the court's own preferences. "

Richard L. Hasen election law expert of the University of California, Irvine says, "the Supreme Court sent the case back to the three-judge court in Texas to redraw congressional and legislative lines using Texas's own plans as a starting point. The Court held that the three-judge court should deviate from Texas's maps only if it is likely that parts of the maps violate the Voting Rights Act. "

Minority advocacy groups are sure to be dismayed by the decision. Joined by the Obama administration, they had argued against the use of the legislature drawn maps at all, arguing that they had not yet been precleared as required by Section 5.

Lurking in the background of this case is a much more controversial question: whether Section 5 of the Voting Rights Act itself violates the Constitution. Critics of the landmark 1965 law say that states who had discriminated in the past should no longer be subject to the part of the law that forces any change in the election process to be cleared by the Department of Justice or a federal Court in Washington, D.C.

Only Justice Clarence Thomas addressed the issue today.  In a concurring opinion Thomas went farther than his colleagues to reiterate his belief that Secton 5 is unconstitutional.