On Wednesday, Washington lawyer Bart S. Fisher wrote to Wolf to say he was granted a license from the Treasury Department, but only to represent Sudan in legal matters, not to lobby. However, Fisher made a case to Wolf that sanctions on Sudan should be repealed.

"By imposing the sanctions mentioned above, the United States has sought to punish and influence the Republic of Sudan," Fisher wrote. "If those sanctions are continued in their current form, however, it is the people of South Sudan who will suffer disproportionately."

Wolf said that's lobbying, and called on Geither in a Thursday letter to repeal Fisher's license.

"[I]n his letter he tries to convince me, as a Member of Congress, that the current sanctions regime should be altered," Wolf wrote to Geithner. "If that's not lobbying, I don't know what is.

"Mr. Fisher should never have been granted a license to begin with," he continued. "But now, it appears that he is in violation of this license. I urge the Department to immediately revoke the license."

Wolf spoke against the license on the House floor on Wednesday.

"We stand just blocks from a museum that cries out 'never again,' " he said Wednesday. "Meanwhile, it appears that this administration is complicit in allowing a genocidal government to have an advocate in Washington."