The director of agriculture shall enforce the provisions of this chapter, and he or she is hereby authorized and empowered to approve and register such brands and labels intended for use under the provisions of this chapter as may be submitted to him or her for that purpose and as may in his or her judgment conform to the requirements of this statute: PROVIDED, HOWEVER, That in any prosecution under this chapter the fact that any brand or label involved in said prosecution has not been submitted to said director for approval, or if submitted, has not been approved by him or her, shall be immaterial.