N.Y.C. Admin. Code § 14-121: § 14-121 Details to special duty.

A transfer, detail or assignment to special duty of any member of the force, except in cases authorized or required by law, shall not hereafter be made or continued, except for police purposes and in the interests of police service. The commissioner, however, whenever the exigencies of the case require it, may make a detail to special duty for a period not exceeding three days, at the expiration of which the member or members so detailed shall report for duty to the officer of the command from which the detail was made.