10 U.S.C. § 12241

(a) The permanent reserve warrant officer grades in each armed force are those prescribed for regular warrant officers by section 571(a) of this title . (b) Appointments in permanent reserve warrant officer grades shall be made in the same manner as is prescribed for regular warrant officer grades by section 571(b) of this title . (c) Appointments as Reserves in permanent warrant officer grades are for an indefinite term and are held during the pleasure of the Secretary concerned.