The department of health and human services shall enforce the provisions of this subdivision and is authorized and empowered to approve such brands and labels intended for use hereunder as may be submitted to it for that purpose and as may in its judgment conform to the requirements hereof; provided that, in any prosecution hereunder, the fact that any brand or label involved in said prosecution has not been submitted to said department for approval, or if submitted has not been approved by it, shall be immaterial.