N.J. Stat. § 34:15-87
No policy of insurance against liability arising under this chapter shall contain any limitation of the liability of the insurer to an amount less than that payable by the assured on account of his entire liability under this chapter, and no provision of such policy shall be construed to restrict the liability of the insurer to any stated business, plant, location, or employment carried on by an assured unless the business, plant, location, or employment excluded by such restriction shall be concurrently separately insured or exempted as provided for in this article.
No such policy of insurance or any indorsement thereon shall insure against any liability whatsoever other than the liability of the employer for compensation under this chapter and for damages imposed by law because of personal injuries, including death at any time resulting therefrom, sustained by his employees.
No action shall be maintained for the collection of premiums on any policy violating any provision of this article. Any policy issued contrary to the provisions of this section shall be construed as incorporating the provisions herein contained. No insurer shall, in action brought upon such policy, plead in defense of such action any provision of such policy which violates any provision of this section.
N.J.S. § 34:15-87