Egypt's top court will on Thursday examine a law which could disqualify one of two presidential candidates, in a legal crisis that threatens to derail an already tumultuous transition from Hosni Mubarak's rule.
The Supreme Constitutional Court is to examine the legality of the political isolation law which bars senior officials of the Mubarak regime and top members of his now-dissolved National Democratic Party from running for public office for 10 years.
The law applies to those who served in the 10 years prior to Mubarak's ouster on February 11, 2011 after a popular uprising.
If approved, the legislation will mean disqualification for Ahmed Shafiq, Mubarak's last prime minister, who faces Muslim Brotherhood candidate Mohammed Moursi in a presidential runoff on Saturday.
Shafiq was initially disqualified from standing in the election in accordance with the law passed by the Islamist-dominated parliament in April.
But in late April the electoral commission accepted an appeal from Shafiq against his disqualification and the case was referred to the court.
On Thursday, the Supreme Constitutional Court will first examine whether the electoral body had the right to refer the case, and if so, will then look into the legality of the text.
The hearing comes two days before the landmark presidential election to choose a successor for Mubarak.
In the first round of voting on May 23 and 24-- which saw 13 candidates compete for the top job-- Moursi won 24.7 percent of the vote, slightly ahead of Shafiq's 23.6 percent.
The race has polarized the nation between those who fear a return to the old regime under Shafiq's leadership and those wanting to keep religion out of politics and who accuse the Muslim Brotherhood -- which already dominates parliament -- of monopolizing power since last year's revolt.
The next president will inherit a struggling economy, deteriorating security and the challenge of uniting a nation divided by the uprising and its sometimes deadly aftermath, but his powers are yet to be defined by a new constitution.
At Thursday's hearing, the court will also examine a High Administrative Court appeal over the constitutionality of aspects of a law governing legislative polls between last November and February that saw Islamists score a crushing victory.