Mississippi's Democratic attorney general says the governor, a Republican, violated the state constitution by vetoing parts of two budget bills.
However, the opinion this week from Jim Hood is non-binding, and it was not immediately clear whether it would have any practical effect.
Hood said it's against the constitution to issue a veto on the conditions of how money can be spent.
July 1 Barbour vetoed part of a bill that dealt with state troopers' pay. He said he didn't want to restrict the efficient management of the Department of Public Safety by mandating the way overtime and compensatory time are handled.
The other partial veto was on a funding bill for the state Motor Vehicle Commission.