CAIRO — Summoned by a decree from the newly elected president, Egypt’s Parliament met on Tuesday for the first time since the nation’s military rulers dissolved it three weeks ago, escalating a power struggle between the Islamist elected officials and the top generals.

In a 15-minute session, the Parliament voted to appeal the court decision authorizing its shutdown, and Egypt’s Constitutional Court, one of three courts considering the issue, later responded with a rebuke insisting that the Parliament remain closed.

The appeal creates a chaotic mess of conflicting legal authorities and jurisdictions that suggests the dispute over the Parliament is unlikely to end any time soon. And it underscored the fact that even 18 months after the ouster of President Hosni Mubarak, both the newly elected Islamists and the military leaders remain determined to seek legitimacy from the existing courts even though they are a vestige of the old Mubarak system.

The newly elected president, Mohammed Morsi of the Muslim Brotherhood, issued a decree on Sunday night calling back the lawmakers, and the generals promptly rejected his order. But indicating some degree of accommodation to the new president, the generals did nothing on Tuesday to stop the mostly Islamist lawmakers from entering the Parliament building. A heavy guard stationed around the building had previously kept them out.

The Supreme Constitutional Court, which issued a hasty ruling authorizing the military’s dissolution of the chamber, fired back with new force. After a daylong emergency session, the court issued a new ruling reinforcing the first, and threatened the new president with the equivalent of contempt of court if he continued to reject its decisions.

“If Morsi does not comply with today’s verdict, he will be liable’’ for defying a court order, said Judge Maher Sami, the official spokesman of the Supreme Constitutional Court, according to the state newspaper Al Ahram.

Ahmed Abo Baraka, a lawyer for the Muslim Brotherhood, called the court’s decision on Tuesday ‘‘political thuggery in the name of the law.’’

A legal adviser to Morsi said the Constitutional Court, which rules on the validity of statutes, did not have the authority to order the dissolution of Parliament no matter what flaws it found in the election law, Al Ahram reported. But the adviser also said it was up to Parliament, not the president, whether it held or discontinued its session.

Morsi had appeared to claim sufficient authority in his decree to undo the generals’ dissolution of Parliament. He said he was merely delaying putting the court’s ruling in place by ordering new elections two months after the ratification of a planned new constitution.

But the Muslim Brotherhood and its lawmakers were not satisfied to convene only on the authority of the presidential decree. Brotherhood lawyers appealed the original decision to the same court that issued it; the Constitutional Court rejected the appeal on Tuesday.

Almost as soon as the lawmakers convened, Speaker Saad el-Katanti of the Muslim Brotherhood held a voice vote approving a new legal appeal of the dissolution to a different high court, the Court of Cassation. He said Parliament respected the Constitutional Court’s determination of principles but wanted ‘‘to find a mechanism to implement those rulings out of respect for the principles of law and the separation of powers.’’

Some of the secular-minded lawmakers opposed to the Brotherhood did not attend the session, showing their support for the military’s dissolution of the Islamist-led body even though it cost their own seats.

Unlike the system in the United States, the Egyptian judiciary has three parallel high courts: a Constitutional Court to review statutes, a Court of Cassation to handle appeals of lower court rulings, and an administrative court that reviews executive actions. With Parliament’s appeal on Tuesday, all three were preparing to weigh in on the dissolution.