A lawyer’s controlling interest in a real estate venture negated his law firm’s malpractice coverage, the Appellate Division, First Department, decided Tuesday.

Ruling in Lee & Amtzis v. American Guarantee and Liability Insurance Co., 653050/11, Justice Judith Gische, writing for a unanimous panel, said the policy’s Business Enterprise Exclusion clause relieved insurer American Guarantee of any obligation to defend the firm and its partners.