Committee chairman Sen. Dick Durbin (D-IL) arrives for a Senate Judiciary Committee business meeting on Capitol Hill on April 4, 2022 in Washington, DC.
CNN  — 

Senate Judiciary Chairman Dick Durbin asked Chief Justice John Roberts or “another Justice whom you designate” to appear before his committee next month for a hearing on Supreme Court ethics rules – a request that is purely voluntary, with Durbin indicating he does not intend to subpoena the justice.

The call for testimony comes after Senate Democrats have raised questions about whether the ethical standards of the high court need to be reviewed or change in the wake of a ProPublica report that found Justice Clarence Thomas has gone on several luxury trips involving travel subsidized by GOP megadonor Harlan Crow.

The hospitality was not disclosed on Thomas’ public financial filings with the Supreme Court, ProPublica said.

Durbin told CNN on Thursday that the committee will not try to subpoena Roberts if he declines the invitation to testify. “No,” Durbin said. “There’s no discussion of subpoenas.”

Such a move would be extraordinary. But even if Democrats wanted to do it, they would have to wait for California Democratic Sen. Dianne Feinstein to return in order to have a chance of getting a majority vote in the committee. Feinstein has been absent as she recovers from shingles.

Republicans on the Judiciary Committee argued that Roberts should reject the request to testify, warning it would be “a circus.”

“I would not recommend the chief accept the invitation because it would be a circus,” Texas Republican Sen. John Cornyn told reporters. “He is a member of a coequal branch of government.”

In his letter, Durbin argued that there is precedent for justices to testify before the committee, citing a hearing in 2011 when then-justices Stephen Breyer and Antonin Scalia appeared for a hearing.

“Since then, there has been a steady stream of revelations regarding Justices falling short of the ethical standards expected of other federal judges and, indeed, of public servants generally. These problems were already apparent back in 2011, and the Court’s decade-long failure to address them has contributed to a crisis of public confidence,” Durbin wrote. “The status quo is no longer tenable.”

The Supreme Court did not immediately respond to a request for comment.

Durbin and Senate Democrats sent a letter earlier this month requesting a review of Thomas’s travel and for Roberts to consider a new ethical standard for the court.

The letter noted that more than a decade ago, members of the committee had written the chief justice “urging the Court to adopt a resolution stating that the Justices of the Court abide by the Judicial Conference’s Code of Conduct for United States Judges – a Code that binds every other judge in the federal judiciary,” Durbin wrote.

Senate Republicans on the committee have not expressed the same level of concern as Democrats, instead defending Thomas and arguing there is no evidence that he violated reporting requirements the courts have in place.

“I probably would (decline) if I were him,” Missouri Republican Sen. Josh Hawley said on Thursday reacting to the news of the request for Roberts to appear before the committee.

“They’ve already done what everybody is complaining about they should have done sooner. If they’ve already done it that’s the end of it,” Iowa Republican Sen. Chuck Grassley said.

Sen. Susan Collins, a Maine Republican who is not on the committee, told reporters that she would need to review the precedent for such a request before commenting.

“I think it’s fine, if he wants to come,” Louisiana Sen. John Kennedy said of the invitation.

“He may not want to come,” Kennedy, a Republican who sits on the Judiciary Committee, added.

Skepticism of Supreme Court assurances it can police itself

A pair of reports in ProPublica this month unveiled that Thomas accepted luxury travel and gifts from Crow – and even a real estate transaction – that went unreported in Thomas’ annual financial disclosures.

Thomas has argued the gifts that were financed by Crow went unreported because he had been advised that he was not required to do so, under an exemption in the court’s disclosure rules for so-called “personal hospitality.”

The undisclosed hospitality – as well as the sale of property Thomas partially owned to Crow – became public not long after Judicial Conference quietly closed a loophole in those rules that appears to have covered some of the hospitality Thomas received. The Judicial Conference updated the disclosure rules under pressure from lawmakers.

Thomas said that he intended to follow that updated guidance in the future, and a source close to the justice also told CNN in recent days that he planned to amend his disclosure form to report the real estate transaction.

With Durbin now inviting Roberts to appear before the committee, Democrats are framing their interest in hearing from him around the broader issue of the Supreme Court’s failure to adopt ethics rules akin to the standards applied to lower courts and other branches of government.

Asked if lawmakers planned to dig deeper into the Thomas allegations, Sen. Mazie Hirono pointed to the investigation Democrats asked Roberts to launch with their Thomas-related letter last week. She told reporters that “really the idea of the code of ethics is what I’d like to get to, in as a cooperative a way as possible.”

“I would hope that [Roberts] would want to come, as a leader of a separate branch of government,” Hirono, a Hawaii Democrat, said.

Thomas’ relationship with Crow is not the only ethics controversy in recent year that has brought scrutiny to the high court. Critics seized on Thomas’ participation in cases connected to the 2020 election after CNN revealed last year that his wife Ginni Thomas exchanged texts with the Mark Meadows – then President Donald Trump’s White House chief of staff – about Trump’s efforts to overturn the 2020 presidential results. The House Judiciary Committee, when it was controlled by Democrats last year, held a hearing on Supreme Court ethics that looked at allegations of a well-financed, secret campaign seeking to influence the high court’s conservatives.

The absence of any reference to ethics, given those controversies, in Roberts’ end-of-the-year report for 2022 was a surprise to some court observers.

In past years, Roberts has stressed the ability of the Supreme Court to police itself, writing in the 2011 report that he had “complete confidence in the capability of my colleagues to determine when recusal is warranted.” His 2021 year-end-report touted the importance of the judicial branch’s “institutional independence.”

Connecticut Sen. Chris Murphy alluded to the court’s assertions that it could manage its own affairs and told CNN, “they have an obligation to come and talk to us.”

“They can solve a lot of this problem by moving forward and adopting code of ethics themselves,” Murphy, a Democrat, said.

This story has been updated with additional information.

CNN’s Manu Raju contributed.