Chief Justice John G. Roberts Jr. on Thursday declined requests to have Justice Samuel A. Alito Jr. recuse himself from cases related to the Jan. 6 Capitol attack after provocative flags flew on the justice’s properties.

The justices make those calls on their own, Chief Justice Roberts wrote in a letter to Democratic senators.

“Members of the Supreme Court recently reaffirmed the practice we have followed for 235 years pursuant to which individual justices decide recusal issues,” he wrote.

The chief justice also rejected a request to meet with Democratic senators to discuss ethics at the Supreme Court, writing that doing so would raise concerns about separation of powers and judicial independence.

Sitting down with leaders of one political party “who have expressed an interest in matters currently pending before the court,” he wrote, would only underscore that “such a meeting would be inadvisable.”

Democratic lawmakers have sounded alarms over ethics and impartiality after revelations in recent weeks that flags displayed outside two of Justice Alito’s residences appeared to back the “Stop the Steal” movement. One, an upside-down American flag, flew over the justice’s front lawn at his Virginia home in January 2021 as the court was considering whether to hear a 2020 election case. The second, an “Appeal to Heaven” flag, a symbol carried on Jan. 6 and associated with a push for a more Christian-minded government, flew at the justice’s New Jersey beach house last summer.

In letter to the chief justice last week, two Democratic senators, Richard J. Durbin of Illinois and Sheldon Whitehouse of Rhode Island, urged Chief Justice Roberts to intervene and to have Justice Alito step aside from two cases related to Jan. 6. One is over whether former President Donald J. Trump is immune from prosecution on charges of trying to overturn the election. The other involves a federal statute used to prosecute hundreds of rioters who ransacked the Capitol.

“By displaying the upside-down and ‘Appeal to Heaven’ flags outside his homes,” the senators wrote, “Justice Alito actively engaged in political activity, failed to avoid the appearance of impropriety and failed to act in a manner that promotes public confidence in the impartiality of the judiciary.”

The court has been under increased scrutiny over ethics questions since revelations last year that Justice Clarence Thomas had failed to disclose decades of luxury gifts and travel from wealthy conservatives. The justices later adopted an ethics code, the first in the court’s history, though it contains no clear enforcement mechanism and does not lay out a structure for any potential consequences or penalties for breaches of the code.

Justice Alito informed Democratic lawmakers on Wednesday that he would not recuse himself from cases arising from the Jan. 6, 2021, attack on the Capitol.

In letters, Justice Alito said that the flags were flown by his wife, Martha-Ann.

“My wife is fond of flying flags,” the justice wrote. “I am not.”

“She was solely responsible for having flagpoles put up at our residence and our vacation home and has flown a wide variety of flags over the years,” he added.

The chief justice did not directly address the flag incidents in his letter, though he noted that Justice Alito had already responded to lawmakers about the issue of potential recusal.