Egyptian President Mohammed Mursi's order to reconvene parliament has been rejected by the country's highest court, which says its ruling dissolving the assembly is binding.Following President Mursi's decree, the speaker of the dissolved house had called for MPs to meet on Tuesday.
Army units outside parliament were withdrawn, allowing MPs to enter.
Mr Mursi, whose Muslim Brotherhood won most seats, says the chamber should function until a new election is held.
But Egypt's Supreme Constitutional Court, meeting on Monday, said that all its rulings and decisions were "final and not subject to appeal".
The Supreme Council of the Armed Forces (Scaf) - whose original decision to dissolve parliament was backed by the court - met in an emergency session shortly after the presidential decree was issued on Sunday.
The new president's order was widely seen as a challenge to the judiciary as well as the military.
Parliament speaker Saad al-Katatni said MPs should return for a session of parliament on Tuesday afternoon, the Mena news agency said.
Despite the apparent tensions, President Mursi and Field Marshal Hussein Tantawi, who heads Scaf, appeared together at a military cadet graduation ceremony on Monday.
New polls The military had enforced a court order last month dissolving parliament because party members had contested seats reserved for independents.
The Scaf took over the reins of power last year, after the revolution that ended former President Hosni Mubarak's 30-year rule.
The army move was initially welcomed by many of the anti-government protesters, but its presence became increasingly unpopular as critics accused its leaders of wanting to hold on to power.
Mr Mursi won the country's first free presidential election last month, and army chiefs formally handed over power on 30 June.
But before his inauguration, the military granted itself sweeping powers.
The commanders' constitutional declaration stripped the president of any authority over the military, gave military chiefs legislative powers, and the power to veto the new constitution, which has yet to be drafted.
In his presidential decree, Mr Mursi said new parliamentary elections would be held 60 days after the constitution had been agreed by referendum.
The Muslim Brotherhood has consistently opposed the decision to dissolve parliament.