MANILA- President Rodrigo Duterte does not have the exclusive authority to decide on treaties entered into by the Philippines, minority senators said Tuesday.

Through their legal counsel, Barry Gutierrez, Senate Minority Leader Franklin Drilon and Senators Francis Pangilinan, Bam Aquino, Leila de Lima, Risa Hontiveros, and Antonio Trillanes IV challenged before the Supreme Court on Tuesday the Philippines' withdrawal from the International Criminal Court.

Pangilinan was the sole petitioner-senator present during Tuesday's oral arguments.

• Supreme Court resumes oral arguments on ICC withdrawal

The senators argued that the withdrawal should be invalidated as the Senate did not concur through a two-thirds vote.

"Nowhere in the Constitution does it say that the President has the sole exclusive authority to withdraw the Philippines from a treaty, much less withdraw unilaterally therefrom without Senate concurrence," Gutierrez told the top court at the resumption of oral arguments on the matter Tuesday.

"It cannot be automatically implied that just because treaty withdrawal involves foreign relations, it is solely an executive prerogative," he added.

Duterte in March pulled out the Philippines from the Rome Statute that created the ICC after the tribunal announced it would initiate a preliminary examination of alleged crimes against humanity under his war on drugs.

Malacañang had earlier insisted that there is no need for a Senate concurrence in the Philippines' withdrawal from the ICC.

"The reason why the Senate consent is not necessary is that the Constitution does not provide it’s necessary. That is a decision to be made by the President as Chief architect of foreign policy,” Presidential Spokesperson Harry Roque, an international law expert, said.

Gutierrez, however, explained the Executive Department cannot simply withdraw from a treaty since this is equivalent to a repeal of a law--which requires Senate concurrence.

In withdrawing the Philippines from the ICC without the concurrence of Senate, Gutierrez said Duterte "infringed on the Senate's treaty powers."

"The reasons for withdrawal mentioned by the President, however, can be easily construed as purely personal to him," Gutierrez said.

• Palace belittles senators’ plea vs ICC withdrawal

The Philippines signed the Rome Statute on Dec. 28, 2000 and ratified and endorsed it in August 2011, during the time of Duterte’s predecessor, the then President Benigno "Noynoy" Aquino III.

The ICC, created through the 1998 Rome Statute, has jurisdiction over 124 of its members, including the Philippines.