WASHINGTON — The US Supreme Court on Tuesday questioned whether federal prosecutors went too far in bringing obstruction charges against hundreds of participants in the Jan. 6, 2021, Capitol riot.

But it was not clear how the justices would rule in a case that also could affect the prosecution of former President Donald Trump, who faces the same charge for his efforts to overturn his election loss in 2020.

The justices heard arguments over the charge of obstruction of an official proceeding in the case of Joseph Fischer, a former Pennsylvania police officer who has been indicted for his role in disrupting Congress’ certification of Joe Biden’s 2020 presidential victory over Trump. Fischer is one of 330 people facing that charge, which stems from a law passed in the aftermath of the Enron financial scandal more than two decades ago to deal with the destruction of documents.

Trump is facing two charges in a separate case brought by special counsel Jack Smith in Washington that could be knocked out with a favourable ruling from the nation’s highest court.

Next week, the justices will hear arguments over whether the former president and presumptive nominee for the 2024 Republican nomination has “absolute immunity” from prosecution in that case, a proposition that has so far been rejected by two lower courts.

Smith has argued separately in the immunity case that the obstruction charges against Trump are valid no matter how the court decides Fischer’s case.

The first former U.S. president under indictment, Trump is on trial on hush money charges in New York and also has been charged with election interference in Georgia and with mishandling classified documents in Florida.

It was not clear after more than 90 minutes of arguments precisely where the court would land in Fischer’s case. Conservative justices Samuel Alito and Neil Gorsuch appeared most likely to side with Fischer, while liberal Justices Elena Kagan and Sonia Sotomayor seemed more favourable to the Justice Department’s position.

Justices Amy Coney Barrett and Ketanji Brown Jackson, a former federal public defender, expressed interest in more of a middle-ground outcome that might make it harder, but not impossible, for prosecutors to use the obstruction charge.

Some of the conservative justices said the law was so broad that it could be used against even peaceful protests and also questioned why the Justice Department has not brought charges under the provision in other violent protests.

“There have been many violent protests that have interfered with proceedings,” Justice Clarence Thomas said.

He was back on the bench Tuesday after an unexplained one-day absence.

Gorsuch appeared to be drawing on actual events when he asked Solicitor General Elizabeth Prelogar whether people could be charged with obstructing an official proceeding if they rose in protest inside the courtroom, heckled the president at the State of the Union or pulled a fire alarm in the Capitol complex to delay a vote in Congress.

Alito, suggesting the government’s reading of the law is too broad, asked whether the charge could be applied to people who disrupted the day’s court session by shouting “Keep the January 6 insurrectionists in jail or ”Free the January 6 patriots.”