N.Y. Second Class Cities Law § 200
The corporation counsel shall be the head of the department of law. He may appoint, to hold office during his pleasure, a first assistant and such other subordinates as may be prescribed by the board of estimate and apportionment. In case of the absence or disability of the corporation counsel, or of a vacancy in the office, the first assistant shall discharge the duties of the office until the corporation counsel returns, his disability ceases or the vacancy is filled. The corporation counsel and first assistant before entering upon the discharge of the duties of their respective offices, shall each execute and file with the city clerk an official undertaking in such penal sum as may be prescribed by the common council.
N.Y. Second Class Cities Law § 200