N.J. Stat. Ann. § 2A:157-22

In any county in which the total number of county detectives and county investigators authorized by this chapter exceeds the total number of officers employed in the prosecutor's office of such county for the detection, apprehension, arrest, indictment and conviction of offenders against the law, as of the effective date of this chapter, no new appointments as county detective or county investigator shall be made, other than to fill vacancies hereafter occurring, without prior approval as to the number and salary thereof by the board of chosen freeholders or, in counties of the first class having a population of less than eight hundred thousand inhabitants, by order of the Superior Court Assignment Judge of the county.