COLUMBIA, S.C. - A Santee Cooper board member who came under fire for his involvement in a study that started as an effort to sell one of the nation's largest public-owned utilities has resigned.

On May 15, Keith D. Munson wrote a letter to Gov. Mark Sanford saying he would resign if a bill changing standards for board members became law.

Sanford's office received the letter Wednesday as the Legislature overwhelmingly overrode Tuesday night's veto of the Santee Cooper legislation.

Munson's resignation letter says the legislation means "it is no longer fair to my family, acceptable to my business, nor beneficial to Santee Cooper for me to remain on the board." In an e-mail, the Greer lawyer told Santee Cooper board members the new law exposes them to fines of $50,000 and court costs.

Munson told The Associated Press last week he'd consider resigning if it would lead to the appointment of John Rainey to the Santee Cooper chairmanship. Rainey, a Sanford ally, previously has been the utility's chairman. Munson also said he'd consider resigning if it would stop the legislation.

That legislation makes finding replacement board members exponentially more difficult, Sanford spokesman Will Folks said. "There's certainly not an incentive for any sane-minded person to sign up for that particular appointment," Folks said.

Munson's resignation makes "it pretty clear there's a problem with the legislation," Folks said. At Santee Cooper's board, "the keys have been effectively handed over to the Legislature," he said.

Munson was closely involved in a Credit Suisse First Boston report released earlier this month that tried to put a value on Santee Cooper's assets. That report started out last fall as an effort to study a potential sale or initial public offering of the utility.

Munson has said he "was the only one who would return CSFBs calls to give them any guidance on the report."

He also wrote an analysis that said the legislation "probably would cause Wall Street to panic." He attached to an April 19 e-mail to Santee Cooper board members and to Lonnie Carter, the utility's chief executive officer.

Munson told Carter "you might want to send to Wall Street since they have not had an opportunity to study the impact of the bill - this might give them a head start." The board's interim chairman, Guerry Green, did that within a couple of hours.

Given Senate opposition, Sanford has withdrawn Green's name from consideration for the chairman's job. On Tuesday, he tapped Oscar Thompson, a Charleston construction company owner, to replace Green, of Pawleys Island.

A Senate panel has been looking at Santee Cooper's board practices and the chairman has said that Green and Munson should be removed from the board. Senate Judiciary subcommittee chairman Luke Rankin, R-Myrtle Beach, has also said a third board member, Richard Coen, should step down.