Wis. Stat. § 103.35
No state office, department, board, examining board, affiliated credentialing board, commission, council or independent agency in the executive branch, the legislature or the courts may, as a condition for receiving an occupational or professional certificate, license, permit or registration, require the submission of information by the applicant which is not essential for the determination of eligibility for the issuance or renewal of the certificate, license, permit or registration. Information which is not essential to determine eligibility for issuance or renewal may be requested but the applicant shall be notified in a prominent place on or accompanying the request that she or he is not required to provide such information.
Wis. Stat. § 103.35