MANILA- The Supreme Court was too deferential to President Rodrigo Duterte when it decided to uphold martial law in Mindanao, a constitutionalist said Friday.

Christian Monsod, one of the framers of the 1987 Constitution, said the high court failed to act as a fact-finding body and instead deferred to the President.

"I think the Supreme Court tended too much to defer to the President and the President’s assessment of the situation without doing their part as required by the Constitution to be in fact, a fact-finding body," Monsod said in an interview on ANC's "Early Edition."

Atty. Christian Monsod says the SC decision on martial law in Mindanao "too deferring to the president." #ANCRecap #ANCEarlyEdition pic.twitter.com/kj3ZIEHqTY

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Duterte placed the entire Mindanao under military rule on May 23 after clashes between government troops and Islamic State-inspired terrorists erupted in Marawi City.

On Tuesday, the High Court affirmed Duterte's declaration, dismissing several petitions that questioned its basis.

In its ruling, 11 magistrates voted to uphold Duterte's declaration over all of Mindanao, while three voted to limit military rule within Marawi City and nearby areas. One justice, meanwhile, voted to nullify the proclamation altogether.

• Read: Supreme Court affirms Mindanao martial law

Solicitor General Jose Calida welcomed the ruling, saying it proved that there was a "real and present rebellion" in Mindanao. The Palace said that the High Court's decision meant that "the whole government now stands together as one against a common enemy."

Both houses of Congress had opted not to hold a joint session to review martial law as majority agreed with the President's declaration.

Monsod said the court was "very liberal" as to the powers of the President under military rule.

"It was too deferring to the President, and the other side of that coin is that the the Supreme court might have abdicated the power and duty given to them by the Constitution to be a trier of facts because they limited themselves to the proclamation and report of the President," he said.

Monsod also emphasized that martial law should only be used sparingly and when necessary. But with the recent Supreme Court ruling, he said the meaning of martial law seemed to have taken a more liberal turn.

"Martial law is supposed to be an instrument of last resort because it is an anomaly within our rule of law," he said.

He added that while petitioners who may seek the court's reconsideration have slim chances of getting the decision overturned, they should still file the plea.

"I think the Supreme Court ignored that by opening the doors this wide for the President. They're actually allowing creeping authoritarianism in our country," he said.