Top House Democrats, including speaker Nancy Pelosi, and the members of the House select committee investigating the January 6 Capitol attack, have been subpoenaed to testify in court in connection with the criminal contempt case against Donald Trump’s one-time chief strategist Steve Bannon.

The subpoenas – which were accepted by the House counsel, Doug Letter, last Friday, according to a source familiar with the matter – compel the handover of documents and testimony about internal decision-making that led to Bannon’s contempt case.

But whether the subpoenas stand depends on how Judge Carl Nichols rules at a hearing next week, where he will asses pre-trial motions. Nichols could decide the testimony of members of Congress, for instance, is inadmissible because of protections like the so-called speech and debate clause.

Bannon’s lawyers are seeking cooperation from top Democrats including Pelosi, the House majority leader Steny Hoyer, the House majority whip Jim Clyburn, all members of the select committee and three select committee counsels, as well as Letter.

The subpoenas request materials that Bannon’s lawyers believe will provide evidence that the select committee did not follow House rules in issuing its subpoena to Bannon last year, and that federal prosecutors violated justice department rules in filing charges.

It was not clear on Tuesday whether Letter, the House counsel, would move to quash the trial subpoenas. Letter, through a spokesman for the select committee, could not be reached for comment.

Letter could also move to reach an arrangement with David Schoen, the lead lawyer defending Bannon in his contempt case. Schoen told the Guardian he would be prepared to discuss the matter in the hope that Letter would not move to dismiss the subpoenas.

“The subpoenas are asking for materials that belong to the American people. It would be pretty ironic for the committee to quash the subpoenas when they issued a subpoena demanding materials from Bannon, where Trump asserted executive privilege,” Schoen said.

Bannon’s lawyers are making a multi-pronged defense to try and save Bannon from being convicted of criminal contempt of Congress after he was referred to the justice department for prosecution for failing to comply with a subpoena in the congressional January 6 inquiry.

The main thrust of Bannon’s argument is that he cannot be held in wilful contempt because he could reasonably believe the subpoena was invalid when the select committee failed to allow a Trump lawyer to attend his deposition, after Trump asserted executive privilege.

The argument rests on a 2019 justice department office of legal counsel opinion that says congressional subpoenas that prevent executive branch counsel from accompanying executive branch employees to depositions are “legally invalid” and not enforceable.

Bannon’s lawyers are also making the case that the select committee in violation of House rules made no effort to grant a one-week extension to reply to the subpoena after his attorney asked for time to review Trump’s related lawsuit against the panel.

The defense that Bannon is advancing – using broad readings of parts of the justice department’s own positions and amalgamating them into a wider argument – is controversial, but it underscores the complexities facing federal prosecutors in pursuing the case.

“Bannon’s trying to use the OLC opinions as a shield that doesn’t quite cover him, but gives him enough of a defense to fend off the DoJ’s necessity of proving criminal intent,” Jonathan Shaub, a University of Kentucky law professor and a former OLC attorney-adviser, previously told the Guardian.