MANILA - Senator Antonio Trillanes IV on Monday said former Defense Chief Voltaire Gazmin had authority to process the amnesty absolving the lawmaker of charges over 2 failed mutinies, contrary to allegations that the latter usurped this power.

President Rodrigo Duterte over the weekend said Gazmin, who investigated Trillanes' case, was also the one who granted the amnesty, when such power is vested in the Commander-in-Chief.

Gazmin signed the certificates of amnesty, making it "void from the beginning," added Chief Presidential Legal Counsel Salvador Panelo on Monday.

• Charges vs Gazmin over Trillanes amnesty 'possible' - Palace
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Trillanes, however, said Gazmin only processed the amnesty in line with a proclamation by former President Benigno Aquino III.

"Hindi naman puwedeng si President Aquino ang magpo-proseso n'yan. Imagine ito ha, iyung absurdity ng kunyari 10,000 o 100,000 ang nag-avail ng amnesty. Na-imagine n'yo ba iyung Presidenteng pipirma ng dokumento," he told reporters.

"Kaya nga may mga executive order na Executive Secretary lang ang pumipirma, as long as delegated s'ya by the President," he added.

(President Aquino could not have processed all of that by himself. Imaging the absurdity if for example there were 10,000 or 100,000 applicants for amnesty. Can you imaging the President signing all of the documents? This is why the Executive Secretary would sometimes sign executive orders as long as he's delegated by the President.)

As a Navy lieutenant, Trillanes and his Magdalo band of soldiers and junior officers occupied the Oakwood Hotel in 2003 and the Manila Peninsula Hotel in 2007 to protest alleged corruption under then President Gloria Macapagal-Arroyo.

Trillanes and several other military rebels were granted amnesty in 2011, leading to his release from detention.

Duterte, in a proclamation released last week, revoked Trillanes' amnesty, saying he did not file an application form and failed to express guilt for his crimes.

Trillanes has asked the Supreme Court to block the President's move. He remains holed up for a week now at the Senate, from where arresting officers have been banned.

• WATCH: Duterte says Trillanes amnesty up to Supreme Court