Minn. Stat. § 181.05: CONSENT OF EMPLOYER TO ASSIGNMENT REQUIRED.

No assignment, sale, or transfer, however made or attempted, of any unearned wages or salary shall be in any manner valid or effectual for the transfer of any salary or wages to be earned or accruing after the making of such assignment, sale, or transfer unless the person, firm, or corporation from whom such wages or salary are to accrue shall consent thereto in writing. Any employer or agent of such employer accepting or charging any fee or commission for collecting the amount due on any such assignment, sale, or transfer shall be deemed guilty of a misdemeanor.