CAIRO (AP) -- Egypt's highest court ruled on Sunday that the nation's interim parliament was illegally elected, though it stopped short of dissolving the chamber immediately, in a decision likely to fuel the tensions between the ruling Islamists and the judiciary.
The Supreme Constitutional Court also ruled that a 100-member panel that drafted the new constitution was illegally elected.
The immediate impact of the ruling is limited. The Islamist-dominated upper house of parliament, called the Shura Council, will remain in place until elections are held for a lower house, likely early next year. The constitution, which was ratified in a nationwide referendum in December with a relatively low turnout of around 35 percent, will also remain in effect.
Still, the opposition said the verdict shows how Islamists' victories at the ballot box are tainted. They argued that the ruling further challenges the legitimacy of the disputed constitution, which was pushed through the panel by Islamists allied to President Mohammed Morsi.
The two sides are squaring off for what may be a major confrontation on the streets by the end of this month.
An activist campaign claims to have collected millions of signatures on a petition demanding Morsi leave office. The organizers plan a massive rally outside the presidential palace on June 30 to mark a year since his inauguration as Egypt's first freely elected president.
"We are paying dearly for the legislative and constitutional absurdity of the Muslim Brotherhood," said prominent commentator and Brotherhood critic Abdullah el-Sinawy. "It is a situation that threatens political problems and dilemmas on the road ahead."
Morsi's backers in the Muslim Brotherhood saw Sunday's ruling as a victory, saying that it implicitly acknowledged the legitimacy of the Shura Council and the constitution because it stopped short of trying to outright abrogate either.
"The ruling turns the page of media controversy over the Shura Council and the constitution," said Brotherhood spokesman Ahmed Aref. "We hope that we never see that page again."
The ruling, according to another Brotherhood figure, senior leader Essam el-Aryan, amounted to "an admission that the constitution came with the will of the people and through a free and clean referendum."
The Supreme Constitutional Court dissolved the Islamist-majority lower house of parliament in June last year, saying the law governing its election was invalid. The court was widely expected to issue a similar ruling dissolving the Shura Council late last year, but Islamist protesters prevented the judges from reaching their chambers when they laid siege to the court's headquarters.
By the time they lifted the siege, the constitutional panel had already adopted the charter in an all-night session, handed Morsi a copy and a referendum was called for its ratification. The new constitution gave legislative power to the normally toothless Shura Council until a new lower house is elected. It also barred the dissolving of the Shura Council.
In both rulings -- the one in June and Sunday's -- the court ruled that the law governing the election of each house of parliament breached principles of fairness because it allowed political parties to run for the third of seats set aside for independent candidaites.
The Shura Council normally does not have lawmaking powers and has long been dismissed as nothing more than a talk shop. Only 7 percent of voters bothered to cast ballots in the elections fort the house, and many of the newborn political parties rooted in the protest movement that toppled Mubarak did not bother to field candidates. The 270-seat chamber is 70 percent Islamist.
Raafat Fouda, a constitutional law professor at Cairo University, pointed to the contradictions at the heart of the ruling, that the Shura Council was illegitimate but will continue to legislate.
"This is one of the wonders of our time that we have been witnessing lately in Egypt," he said. "It is certainly the result of the pressures and the terrorism the Constitutional court has been subjected to."
However, law lecturer and former legislator Ehab Ramzy said the ruling was expected since the new constitution shielded the Shura Council from dissolution.
But, he added, it could be a prelude to future, unfavorable rulings against the chamber.
The Shura Council's critics say it is ill-equipped to be the nation's sole law-making body, and complain that it's considering legislation that will have a far reach into the future rather than pass only what is absolutely necessary during the transition period.
The ruling on the legitimacy of the constitutional panel may not have any impact on the charter itself. But it could raise future questions on its legal foundations. Critics say the charter restricts freedoms and gives clerics a say in legislation. The Islamists who drafted it hail the document as the best one Egypt has ever had.