Maria Lourdes Sereno's colleagues voted on Friday to remove her as Supreme Court chief justice in an unprecedented decision that has sparked a legal firestorm.
"She will file MR (motion of reconsideration)," her spokesman Carlo Cruz said in a message to AFP without elaborating.
Duterte had openly called for Sereno's removal from the court, calling her an "enemy" after they clashed over his bloody war on drugs and alleged abuse of power.
Sereno's expulsion came due to a petition by the chief government lawyer -- a Duterte appointee -- who argued that she was not qualified for her position and accused her of not filing statements of assets and liabilities in previous years -- accusations she categorically denied.
Legal experts, including other Supreme Court judges, have argued that Sereno's sacking is a violation of the constitution, which says a justice can only be removed through impeachment in Congress.
In opinions released Saturday, dissenting judge Marvic Leonen called the move "a legal abomination" while fellow justice Alfredo Benjamin Caguioa said, "this case marks the time when the Court commits seppuku (ritual suicide) - without honour".
Pacifico Agabin, an expert in constitutional law at the University of the Philippines College of Law, told AFP Sereno's appeal was unlikely to succeed, saying: "I don't think any one of the justices will have a change of mind".
Sereno, who has urged her supporters to "fight for justice and demand accountability", is the latest high-profile critic of Duterte to be targeted after speaking out against the president.
Other Duterte critics have also been ousted, punished or threatened, including Senator Leila de Lima who has been jailed, the Commission on Human Rights and an anti-corruption prosecutor who investigated allegations that Duterte has hidden wealth.
Duterte has faced global criticism for human rights abuses particularly related to his bloody campaign against illegal drugs which police say has claimed the lives of around 4,200 suspects in nearly two years. Rights groups allege the actual number is three times higher.
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