Washington (CNN) -- A liberal reform group has asked the Justice Department to investigate allegations of conflict of interest by Supreme Court Justices Antonin Scalia and Clarence Thomas.
Washington-based Common Cause filed a petition Thursday with the Obama administration, urging that a controversial campaign finance reform decision be vacated because, the group says, the justices attended closed-door political gatherings sponsored by two top Republican donors and industrialists.
The request for a government probe comes exactly a year after the Supreme Court's key ruling giving corporations -- businesses, unions, and advocacy groups -- more power to spend freely in federal elections, overturning long-standing congressional restrictions.
"It appears both justices have participated in political strategy sessions, perhaps while the case was pending," said the Common Cause petition, "with corporate leaders whose political aims were advanced by the decision."
The self-described "non-partisan, grass-roots organization" wants a fact-finding investigation to determine the extent of Scalia's and Thomas's participation, and to recommend the so-called "Citizens United" decision be nullified if any impropriety is uncovered.
In a conference call with reporters, Common Cause officials had few specifics on what the justices may have discussed at the private retreats, and when. But the New York Times reported invitations for a political retreat next week in California --sponsored by the same two GOP donors -- mentioned past appearances by "notable leaders" like Scalia and Thomas, two of the most conservative justices on the nine-member court.
All federal judges are required to list on annual financial disclosure forms any out-of-town travel paid by private groups for speeches and other appearances. Both justices listed separate trips in 2007 and 2008 for gatherings they said were sponsored by the Federalist Society, a conservative legal group with reported ties to David and Charles Koch, who head their family-run energy company based in Wichita, Kansas. Koch Industries is one of the largest privately held firms in the United States.
Media reports in the past have mentioned Scalia's and Thomas's ties to the Kochs.
"We believe it is inappropriate for a Supreme Court judge to be 'featured' at or attend closed-door strategy meetings with political donors, corporate CEOs, candidates and political officials, and thereby lend the prestige of their position to the political goals of that event," Common Cause argues in its petition. "A reasonable person would question the impartiality of Justices Thomas and Scalia in the Citizens United case based on their attendance at political strategy meetings sponsored by a corporation that raises and spends millions to defeat Democrats and elect Republicans."
There was no immediate reaction from the high court or the Justice Department about the request for a government probe.
The Common Cause petition is, even by the group's own admission, a long shot, since the Justice Department cannot compel any recusal, or vacate any decision. Separation of powers gives federal judges latitude to decide for themselves whether to pull of out a case.
Supreme Court justices are not bound by the same code of conduct as other federal judges, but judicial officials have said the high court uses those rules as guidance.
Scalia refused to withdraw from a 2004 court appeal over whether then-Vice President Dick Cheney should have to disclose documents related to an energy task force he headed in the White House. Scalia had gone on a private hunting trip with Cheney while the case was being considered, leading to an appearance of conflict existed.
But a year earlier Scalia did recuse himself in a court case over having children recite the Pledge of Allegiance in public schools. The 74-year-old justice had made general remarks on separation of church and state at a Religious Freedom Day rally some months before.
Common Cause also noted Clarence Thomas' wife, Virginia, is a leading conservative political activist who in 2009 formed an advocacy group active in a range of hot-button issues, including health care reform. Virginia Thomas no longer has a leadership role in Liberty Central, but remains an adviser to the group.