N.C. Gen. Stat. § 58-73-20: Company not to plead ultra vires.

Any company which executes any bond, obligation or undertaking under the provisions of this Article is estopped, in any proceeding to enforce the liability which it assumes to incur, to deny its corporate power to execute such instrument or assume such liability. (1899, c. 54, s. 49; 1901, c. 706, s. 1, subsec. 5; Rev., s. 275; C.S., s. 342.)