WASHINGTON – The Supreme Court yesterday threw out part of a Texas congressional map engineered by a former House majority leader, Tom DeLay, saying some of the new boundaries failed to protect minority voting rights.

The decision was a small victory for Democratic and minority groups who accused Republicans of an unconstitutional power grab in drawing boundaries that booted four Democratic incumbents out of office.

The ruling did not make clear whether lower courts or the state would have to change congressional district boundaries before the November elections.

Justice Kennedy, writing for a 5-4 majority, said Hispanics do not have a chance to elect a candidate of their choosing in south and west Texas under the state’s plan.

The plan’s “troubling blend of politics and race – and the resulting vote dilution of a group that was beginning to achieve [the federal law’s] goal of overcoming prior electoral discrimination – cannot be sustained,” Justice Kennedy wrote.

Some 100,000 Hispanics had been shifted out of a district represented by a Republican, and foes of the plan had argued it violated the Voting Rights Act, which protects minority voting rights.

Republicans picked up six Texas congressional seats two years ago and the court’s ruling does not seriously threaten those gains.

The court ruled 7-2 that state legislators may draw new congressional maps anytime – not just once a decade as Texas Democrats had claimed and has been traditional nationwide. That means any state’s lawmakers can push through new maps anytime there is a power shift in the legislature.

The Constitution says states must adjust their congressional district lines every 10 years to account for population shifts. In Texas the boundaries were redrawn twice after the 2000 census, first by a court, then by state lawmakers in a second round promoted by Mr. DeLay after Republicans took control.

That was acceptable, the justices said.

Two years ago, justices split 5-4 in leaving a narrow opening for challenges claiming party politics overly influenced election maps.

The court was also fractured yesterday with six separate opinions.

The court’s four most conservative members opposed the part of the decision that found a violation of the Voting Rights Act.

Justice Scalia complained the court should have shut the door on all claims of political gerrymandering in map drawing. Justice Stevens took the opposite view.

“By taking an action for the sole purpose of advantaging Republicans and disadvantaging Democrats, the state of Texas violated its constitutional obligation to govern impartially,” he wrote.

Justice Kennedy’s decision did not specify how quickly the lines of District 23 must be redrawn, but he said more than one district would be affected.

Angela Hale, a spokeswoman for the Texas attorney general, said, “The timeline and the procedure for redrawing the only district requiring further action will be addressed by the three judge federal district court at a hearing in the near future.”

The court also ruled against two foreign suspects who argued an international treaty required police to inform them they had a right to contact their governments when they were arrested. By a 6-3 vote, justices did not decide whether a 1969 treaty signed by America and other countries requires suspects to be informed of such a right.

And the court ruled that Pennsylvania officials did not violate the free speech rights of troublesome inmates by keeping secular newspapers and magazines away from them. Justices, by a 6-2 vote, said the state could use newspapers as incentives to get inmates to behave.