Sen. Dick Durbin (D-Ill.), chair of the Senate Judiciary Committee, sent a letter Thursday to Chief Justice John Roberts asking him to answer questions related to the Supreme Courts ethics policies.

The letter, signed by all 11 Democrats on the Judiciary Committee, comes on the heels of Roberts rejection of Durbins request that the chief justice appear, or designate another justice to appear, before the committee for a hearing about how the court polices conflicts of interest and other ethics issues.

The court is currently roiled by ethical controversies after ProPublica wrote about how Justice Clarence Thomas failed to report hundreds of thousands of dollars in gifts from billionaire conservative donor Harlan Crow, along with the sale of property to Crow. In addition, despite an insistence by Crow and Thomas that Crow never had business before the court, reports show that the court did decide whether to hear a case brought against one of his companies while his financial interests were relevant to cases before the court .

Justice Neil Gorsuch also failed to list the purchaser of a sale of more than $1 million in property to the chief executive of a law firm that routinely has business before the court, according to a report by Politico .

In rejecting the committees request to appear or to send a justice to appear for a hearing, Roberts attached a Statement of Ethics Principles and Practices to which all of the current Members of the Supreme Court subscribe.

The statement of principles raises more questions than it resolves, and we request that you respond to several key questions, according to the response from Durbin and the Judiciary Committee Democrats.

The court does not have a binding code of conduct, as the lower federal courts do, and is opaque in handling ethics issues when they arise. Durbins letter probes into the courts lack of transparency.