Former Senate President Franklin Drilon on Thursday defended the 12-senator quorum that removed Alan Peter Cayetano from the Senate leadership, citing a landmark Supreme Court ruling and a similar situation during his tenure as Senate president.

In a radio interview, Drilon said the newly formed majority under acting Senate President Sherwin Gatchalian acted within parliamentary rules when it declared leadership positions vacant.

He cited the 1949 Supreme Court case Avelino v. Cuenco, which held that lawmakers outside the Senate's “coercive jurisdiction” are excluded from the quorum count because they cannot be compelled by the chamber to attend sessions.

According to Drilon, the Senate's effective membership was reduced from 24 to 22 because Jinggoy Estrada remains detained on a non-bailable plunder charge while Ronald dela Rosa is reportedly evading an international arrest warrant.

“If we say the number is 24, the quorum should be 13. But according to the Supreme Court decision, the count of senators should only be those within the jurisdiction of the Senate,” Drilon said.

He also recalled a similar situation in 2015 when the Senate operated with only 17 available members because several senators were either abroad or incarcerated.

“The rule then was 12 was already a quorum, and that is exactly what happened now,” Drilon said.

Drilon maintained that the 12 senators present during Wednesday's session had the authority to declare leadership positions vacant, arguing that doing so was necessary to prevent the Senate from becoming paralyzed by political boycotts.

However, he reiterated that while 12 senators may constitute a quorum and remove officials, they cannot elect a permanent Senate president because the Constitution requires 13 votes to do so.

As a result, Drilon said Gatchalian's assumption as acting Senate president was procedurally proper after he was elected Senate president pro tempore, the position next in the line of succession under Senate rules.

Drilon also questioned efforts by the Cayetano bloc to continue conducting official Senate business. Referring to a Blue Ribbon Committee hearing scheduled by Sen. Pia Cayetano, he noted that Gatchalian's work-from-home directive for Senate employees meant no official secretariat would be present to record proceedings.

“There is no administrative staff in the Senate today. So whoever goes, without administrative staff to record the events, then in the records of the Senate, no hearing took place,” Drilon said.

He added that a similar situation occurred during his term as Senate president, when sessions held without recognition from Senate leadership were not officially recorded in the chamber's proceedings.