Madison Square Garden Chief Executive James Dolan has agreed to pay a $610,000 penalty for violating security reporting rules.

Dolan, whose company owns the NY Knicks and the NY Rangers, acknowledged the violation on Thursday and blamed it on the law firm responsible for reporting his MSG shares.

The firm, Debevoise & Plimpton, “inadvertently missed” a deadline for the filing of voting shares acquired by Dolan, according to an MSG statement. “Debevoise agreed to pay the fine,” it added.

Under the Hart-Scott-Rodino Act, shareholders whose holdings exceed certain thresholds must notify regulators of plans to raise their voting shares above certain dollar amounts and then observe a waiting period before completing their transactions.

The Federal Trade Commission alleged Dolan violated the HSR Act from September 2017, when he acquired additional MSG voting shares, through December 2017, when the waiting period for those shares expired.