The high court is an elite institution with just nine members serving lifetime terms; it's also unique because of what it lacks.

"The Supreme Court is not subject to the code of conduct that applies to every other single judge in the federal system," said Caroline Fredrickson, a visiting professor at Georgetown University Law Center.

Nonprofit news outlet ProPublica reported last week that Thomas accepted a series of luxury trips for nearly two decades paid for by Harlan Crow, a Republican megadonor, which the justice never listed on his annual financial disclosure forms.

"One of the issues that's highlighted here is [that] the disclosure laws are not enough," said Fredrickson.

Democrats, including North Carolina Rep. Deborah Ross, are demanding that Congress pass a code of ethics for Supreme Court justices.

"I believe that the Supreme Court should be held to the same standards that members of Congress are held to," Rep. Ross, a member of the House Judiciary Committee, told Spectrum News.

Ross was one of nearly two dozen House and Senate Democrats who penned a letter to Chief Justice John Roberts last week calling for an investigation into trips taken by Justice Thomas.

"Remember this: they are lifetime appointments," she said. "Members of Congress have to face the voters on a regular basis. But if you have a lifetime appointment, you must be held to the highest standard of accountability."

Fredrickson said that such a code of ethics could include:

• Stricter regulations on the disclosure of gifts;
• A more transparent recusal process when justices have a conflict of interest in a case, and;
• Stricter rules regarding family members involved in political activities connected to cases before the court.

"Everyone else in the federal government has been able to survive with conflict of interest rules, and with ethics rules, and with disclosure rules," said Fredrickson. "And if our Supreme Court can't abide by those kinds of limitations, well, I think maybe they need to find another job."

The court could create its own written code but hasn’t done so. If one is created, it’s unclear how the rules would actually be enforced, though impeachment by Congress is an option.

Spectrum News has reached out to the office of Sen. Thom Tillis, R-N.C., a member of the Senate Judiciary Committee, to see if he supports efforts to adopt a code of ethics but hasn't heard back.