Egypt's Islamist putschdeclared himself a dictator.
Egypt's President Mohammed Mursi has issued a declaration banning challenges to his decrees, laws and decisions.
The declaration also says no court can dissolve the constituent assembly, which is drawing up a new constitution.
President Mursi also sacked the chief prosecutor and ordered the retrial of people accused of attacking protesters when ex-President Mubarak held office.
Egyptian opposition leader Mohammed ElBaradei accused Mr Mursi of acting like a "new pharaoh".
In a joint news conference held late on Thursday, Mr ElBaradai and other opposition figures described the declaration as a "coup against legitimacy" and called on Egyptians to take to the streets in protest.
The declaration also gives the 100-member constituent assembly two additional months to draft a new constitution, to replace the one suspended after President Mubarak was overthrown.
The re-write of the constitution, which was meant to be finished by December, has been plagued by dozens of lawsuits questioning the make-up of the constituent assembly.
Once completed, the document should then be put to a referendum. If it is approved, legislative elections will be held two months later.
Last month, the Supreme Constitutional Court rejected a first draft released by the assembly, saying that it tried to limit the courts' powers and interfere in judicial affairs.
But Mr ElBaradei said the decree effectively placed the president above the law.
"Mursi today usurped all state powers and appointed himself Egypt's new pharaoh. A major blow to the revolution that could have dire consequences," the Nobel Peace Prize winner wrote on his Twitter account.
The vice-president of the Supreme Constitutional Court, Tahani al-Gebali, told the Spanish news agency Efe that Mr Mursi was now an "illegitimate president".
The Egyptian Judges' Club has called an extraordinary meeting to discuss Mr Mursi's decision. "The state of law is at stake," the association said in a public statement.
Meanwhile Heba Morayef, the Egypt director for Human Rights Watch, said that while the country needed judicial reform, "granting the president absolute power and immunity is not the way to do it".It will be interesting to see how the Obama administration reacts to this and whether Congress tries to place conditions on Egypt's aid money. But from Israel's perspective this proves, yet again, how fragile the Camp David Treaty is and how foolish the Americans were to abet throwing Mubarak out.
Oh yeah - it also proves that elections do not make a democracy. You'd think the Americans would have learned that by now.