Changing the locks on rental property during the course of a tenancy is quite possibly the dumbest thing a landlord could do. Doing so is a HUGE no-no, and it's something Minnesota statutes and the courts take very seriously. If a landlord skips the eviction process and just changes the locks, he or she can be in for a world of hurt. In that scenario, a tenant can immediately bring an ex parte lock-out petition and eventually recover treble damages along with attorney's fees.
However, that's not the only ramification. Intentionally removing a tenant from rental property is one of the few criminal provisions found in chapter 504B of the Minnesota statutes (the landlord/tenant chapter). Anyone who does this can be prosecuted for a misdemeanor and risks going to jail for up to 90 days as well as a $1,000.00 fine.
Despite these consequences, landlords still do this from time to time. Often it's because the landlord is ignorant of the law or possibly doesn't even realize he or she is a landlord (such as a case where a relative has been staying on the couch for a few weeks). But sometimes, it's just plain old fashioned arrogance. Whatever the motive, locking out a tenant is wrong, illegal, and, yes, a crime in the state of Minnesota.