The Senate impeachment court cannot compel the attendance of Senators Jinggoy Estrada and Rodante Marcoleta, both detained on plunder charges, at the ongoing trial of Vice President Sara Duterte, as insisting on doing so would breach the separation of powers between the branches of government, a former law dean warned Tuesday.

Lawyer Mel Sta. Maria, former dean of the Far Eastern University Institute of Law, made the statement in response to Senator Alan Cayetano’s recommendation to ask the Sandiganbayan to allow Estrada and Marcoleta to perform their duties as senator-judges — given that they could eventually be released on bail or have their cases dismissed.

Sta. Maria argued that since the lawmakers were incarcerated, they had been stripped of their liberty and were “constrained” by legal limitations.

He pointed to Supreme Court jurisprudence that limits the legislative duties of detained lawmakers, as evidenced by prior rulings involving former senators Sonny Trillanes IV and Leila de Lima.

“The spirit of the law is, if you’re already in jail you do not have the same rights as other people. You are limited by the law,” he said on ANC’s Headstart.

Assuming that the Sandiganbayan would be lenient and permit them to attend the trial in person under police escort, they would be restricted from exercising their legislative duties or functioning as senator-judges, including participating in the voting, according to Sta. Maria.

This restriction, he emphasized, shall be strictly enforced even if the Senate impeachment court passes a resolution supported by a majority of the senators.

Estrada has been detained since 1 June, while Marcoleta was arrested hours before the impeachment trial began on Monday.

Due to a 90-day preventive suspension imposed by the anti-graft court, Estrada was barred from performing his duties pending the investigation.

Cayetano, however, argued that the impeachment court is sui generis, or a class of its own, separate from the Senate as a legislative body.

As a result, he pointed out, senators should be permitted to fulfil their mandate as judges in an impeachment trial, as their absence would effectively amount to an acquittal vote, undermining the principles of a fair trial.

On the other hand, Sta. Maria contended that the Senate, though sitting as an impeachment court, is not the judiciary; therefore, it has “no power” to override judicial detention orders.

If it insists on that, he warned that the separation of powers between the legislature and the judiciary will be breached.

“They are not empowered to do so, and they cannot intrude into the exclusive domain of the courts,” he stressed.

Although Marcoleta has not been meted out a preventive suspension, Sta. Maria averred that this does not constitute an assurance that the Senate impeachment court could compel his participation, because only the Sandiganbayan has the discretion to grant such permission.

According to Sta. Maria, only the courts, in this case the Sandiganbayan, have authority over the detained senators.

Therefore, the decision on whether Estrada and Marcoleta could participate in the impeachment trial while under detention rests solely with the Sandiganbayan, and the Senate impeachment court must abide by whatever the court orders.

On the second day of the impeachment trial on Tuesday, Cayetano reiterated that “if they are not allowed to vote, then that will be counted as a vote for acquittal, and that might be favorable to the defense rather than a part of giving a fair trial.”