Supporters of Morsi, who hails from the Islamic fundamentalist Muslim Brotherhood, claim that the court's judges remain loyal to Mubarak, who appointed them, and accuse them of trying to derail Egypt's transition to democratic rule.
In addition to the high court's expected ruling Sunday on the legitimacy of the constitution-drafting panel, it was also expected to rule on another body dominated by Morsi supporters, parliament's upper chamber.
Though Morsi's Nov. 22 decrees provide immunity to both bodies against the courts, a ruling that declares the two illegitimate would have vast symbolic significance, casting doubt on the standing of both.
The Brotherhood's political arm, the Freedom and Justice party, sought to justify the action of its supporters outside the court as a peaceful protest. It reiterated its charge that some members of the judiciary were part and parcel of Mubarak's autocratic policies.
"The wrong practices by a minority of judges and their preoccupation with politics ... will not take away the respect people have for the judiciary," it said.
Its explanation, however, failed to calm the anger felt by many activists and politicians.
"President Morsi must take responsibility before the entire world for terrorizing the judiciary," veteran rights campaigner and opposition leader Abdel-Halim Kandil wrote in his Twitter account about the events outside the constitutional court.
Liberal activist and former lawmaker Amr Hamzawy warned what is ahead may be worse.
"The president and his group (the Muslim Brotherhood) are leading Egypt into a period of darkness par excellence," he said.
"He made a dictatorial decision to hold a referendum on an illegal constitution that divides society, then a siege of the judiciary to terrorize it."
Egypt has been rocked by several bouts of unrest, some violent, since Mubarak was forced to step down in the face of a popular uprising. But the current one is probably the worst.
Morsi's decrees gave him powers that none of his four predecessors since the ouster of the monarchy 60 years ago ever had. Opposition leaders countered that he turned himself into a new "pharaoh" and a dictator even worse than his immediate predecessor Mubarak.
Then, following his order, the constituent assembly rushed a vote on the draft constitution in an all-night session.
The draft has a new article that seeks to define what the "principles" of Islamic law are by pointing to theological doctrines and their rules.
Another new article states that Egypt's most respected Islamic institution, Al-Azhar, must be consulted on any matters related to Shariah law, a measure critics fear could lead to oversight of legislation by clerics.
Rights groups have pointed out that virtually the only references to women relate to the home and family, that the new charter uses overly broad language with respect to the state protecting "ethics and morals" and fails to outlaw gender discrimination.
At times the process appeared slap-dash, with fixes to missing phrasing and even several entirely new articles proposed, written and voted on in the hours just before sunrise.
The decrees and the vote on the constitution draft galvanized the fractured, mostly secular opposition, with senior leaders setting aside differences and egos to form a united front in the face of Morsi, whose offer on Saturday for a national dialogue is yet to find takers.
The opposition brought out at least 200,000 protesters to Cairo's Tahrir Square on Tuesday and a comparable number Friday to press demands that the decrees be rescinded.
The Islamists responded Saturday with massive rallies in Cairo and across much of Egypt.
The opposition is raising the stakes with plans to march on Morsi' palace on Tuesday, a move last seen on Feb. 11, 2011 when tens of thousands of protesters marched from Tahrir Square to Mubarak's palace in the Heliopolis district to force him out. Mubarak stepped down that day, but Morsi is highly unlikely to follow suit on Tuesday.
