No person may perform motor vehicle repair that releases or may release refrigerant from a mobile air conditioner or trailer refrigeration equipment or may install or service a mobile air conditioner or trailer refrigeration equipment that contains refrigerant unless that person is properly trained and certified in appropriate programs, as specified by the federal environmental protection agency under 42 USC 7671h.
Wis. Admin. Code Department of Agriculture, Trade and Consumer Protection ATCP 136.08
A list of currently authorized Mobile Air Conditioning Technician Training and Certification programs can be found here: https://www.epa.gov/section608/section-608-technician-certification-programs and here: https://www.epa.gov/mvac/section-609-technician-training-and-certification-programs