South Carolina Governor Mark Sanford broke the law when he bought more-expensive airline seats with taxpayers' money, according to the leader of a state senate committee investigating the infractions. State Sen. David Thomas, a Greenville Republican, said Sanford violated state laws when he didn't purchase the cheapest travel possible, which cost the state $13,700 more than if he had bought available economy seats. "It could be perceived, if it's significant enough and a case can be made of it, to constitute a case for possible impeachment," Thomas said Monday. Legislators might seek other sanctions on Sanford, such as asking him to reimburse the state. Sanford acknowledged visiting his Argentine mistress on one of the trips where he flew business class despite available economy seats. He reimbursed the state for part of that trip after it came under public scrutiny in June, so Thomas said that trip is not under investigation.