Duterte also ordered the justice department and the military to pursue criminal and administrative complaints against Trillanes, a former navy officer.

“With our MPs (military police) and legal officer in the Senate, we are awaiting to acquire his custody for the purpose of returning him to military control and for him to face a court martial,” Defence Department spokesman Arsenio Andolong told reporters.

Trillanes had told the police and military not to follow Duterte’s “illegal order” for him to be arrested without a court warrant, saying his rebellion and coup cases were dismissed in 2011 without being questioned by the government after he was availed of an amnesty offered by Duterte’s predecessor.

Addressing military and police officers who may be pressured to enforce Duterte’s order out of fear, Trillanes said, “Duterte will not be there for long, please do not do anything illegal or unconstitutional.”

Duterte’s order, which was made public on Tuesday while he was on a trip to Israel, has sparked a legal debate. Some legal experts have questioned whether Duterte can invalidate a rebel amnesty declared by a previous president and approved by legislators.

Duterte orders arrest of Philippine Senator Antonio Trillanes

Justice Secretary Menardo Guevarra said on Tuesday that Duterte voided Trillanes’ amnesty because the senator had failed to comply with all of its requirements, including a clear admission of his involvement in past coup attempts.

Trillanes cannot invoke his congressional immunity from arrest because the crimes he allegedly committed, including rebellion, were serious and punishable by life imprisonment, Guevarra said.

During a televised Senate session, however, Trillanes showed video footage and news reports denying Duterte’s basis for voiding his amnesty. The news reports showed an image of his amnesty application, which officials said they could not find, and carried remarks by Trillanes acknowledging his participation in the uprisings.

“That presidential declaration should alarm the justices of the Supreme Court because Duterte there exercises executive, legislative and judicial powers,” Trillanes said. “If they affirm the presidential declaration, the president can issue warrants of arrest.”

Despite questions on Duterte’s move, military spokesman Colonel Edgard Arevalo earlier said Trillanes “will be reverted to his status as active military personnel subject to military law and military discipline”.

A military court may be reconstituted to try Trillanes after his amnesty was voided, Arevalo told reporters.

Philippine President Rodrigo Duterte blames ‘beautiful women’ for rape cases

The 47-year-old former navy officer was detained for several years before his election to the Senate for involvement in three military uprisings from 2003 to 2007 to protest government corruption.

Duterte has openly expressed anger against Trillanes, who has accused him of large-scale corruption and involvement in illegal drugs. The volatile president has repeatedly denied the allegations.

Aside from Trillanes, another opposition senator, Leila De Lima, has been detained after being accused by Duterte of involvement in illegal drugs, a crime she has vehemently denied. A former human rights commission chief, De Lima investigated Duterte’s alleged role in extrajudicial killings in a years-long anti-drug crackdown when he served as mayor of southern Davao city for years.

Another Duterte critic, Maria Lourdes Sereno, was ousted by fellow justices from the Supreme Court in May after the government alleged that her appointment by Duterte’s predecessor was legally flawed and petitioned for her removal.