The Oklahoma Supreme Court heard arguments Tuesday on three revenue-raising measures the state legislature passed in the final days of the session.
The Justices will decide if the measures are constitutional.
One changes motor vehicle taxes, and the other adds a fee to cigarette purchases.
The state's constitution says lawmakers can't pass any new taxes in the last five days of a session.
All three of the measures came during that time period.
"This bill was passed, not figuratively but literally at the 11th hour, obviously not within five days," said Clyde Muchmore, Oklahoma Automobile Dealers Association Attorney.
The state argues the measures aren't new taxes, but either modifications to existing taxes or just fees.