This is a ruling that will have an important impact on House races later this year.

The Supreme Court on Friday instructed a lower court in Texas to take a fresh look at election maps it had drawn in place of a competing set of maps from the Texas Legislature. The justices said the lower court had not paid enough deference to the Legislature’s choices and had improperly substituted its own values for those of elected officials.

The court’s unanimous decision extends the uncertainty surrounding this major voting-rights case, which could help determine control of the House of Representatives.

“To avoid being compelled to make such otherwise standardless decisions,” the Supreme Court’s unsigned decision said, “a district court should take guidance from the state’s recently enacted plan in drafting an interim plan. That plan reflects the state’s policy judgments on where to place new districts and how to shift existing ones in response to massive population growth.”

When the legislature drew its map, officials, not surprisingly, went out of their way to help Republican candidates. A special three-judge federal court said those district lines were discriminatory and drew a fairer map, intended to increase the voting power of Texas’ growing Hispanic population.

The result was a map that likely would have given Democrats at least four additional U.S. House seats, just from the Lone Star State, and in a competitive cycle, that increased the odds of Democrats reclaiming a House majority. Today’s Supreme Court ruling rejected that map.

The process is not yet over — it’s now unclear where Texas’ lines will be for 2012 races — but the high court’s unanimous decision will no doubt come as a relief to Republicans.

Postscript: And by the way, speaking of the federal judiciary, if you’re wondering what the courts might look like if President Obama loses in November, Dahlia Lithwick has a great story in the new print edition of the Monthly.

Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.