A Nassau County lawmaker pleaded not guilty in court after turning himself in to the FBI this morning.

Nassau Legislator David Denenberg surrendered to the FBI in Melville and was arraigned on mail fraud charges.

Denenberg is accused of billing a client at his former law firm more than $2 million for work never performed. The firm also filed a lawsuit against Denenberg related to the allegations. The move caused Denenberg to drop out of the state Senate race last month.

In court, Denenberg's attorney Jason Russo entered a plea of not guilty. Russo called the case a "misunderstanding" and said Denenberg will voluntarily repay some of the money. 

"We've resolved one aspect of this already, we'll resolve this with the government I'm sure expeditiously," said Russo.

Following the court appearance, Denenberg's wife Kara left the courthouse separately, wearing a Batman mask. Denenberg apologized for the legal mess.

"I apologize that we've all been going through all of this, but throughout this time, I haven't made comments about allegations because it's not to anyone's benefit for me to be trying a case in the press," he said.

Denenberg posted a $500,000 bond and will return to court Dec. 11.