WASHINGTON — A federal judge in Wisconsin has challenged the Securities and Exchange Commission over a proposed settlement of fraud charges against a publicly traded company, citing as a precedent the agency’s pending case against Citigroup.

That represents a significant expansion of the impact of the Citigroup case, in which Judge Jed S. Rakoff of the Federal District Court in New York threw out a proposed settlement between the company and the S.E.C.

Judge Rakoff said he had rejected the Citigroup settlement because there were no established facts on which to base a decision whether the settlement was “fair, reasonable, adequate and in the public interest.”

At the time of the November decision, lawyers who were watching the case noted that the ruling did not constitute a precedent that would bind other judges in New York or elsewhere.