Heads up: The U.S. Supreme Court and many lower U.S. District Courts since then have ruled that rental inspections are legal and municipalities may carry out an inspection program and require registration and certification. However, a municipality cannot force their way in--they must have the tenant's permission (not the owner's). If the tenant does not give permission, the municipality can do one of two things: get an administrative warrant (which does not require probable cause) or wait until the unit is vacant. Also, the municipality cannot penalize the tenant or the property owner for the tenant exercising their right to refuse, i.e. fine, fee or condemn the property simply for the failure of the tenant to give permission. All of this is required in order to protect the tenant's 4th Amendment rights.
One particular and fairly recent case in Flint, Michigan found that the City of Flint was incorrectly carrying out their rental inspection program by not allowing for tenant's refusal and specifically stating in their ordinance that an administrative warrant was necessary where the tenant refused--if the inspection was not an emergency. The City subsequently changed its ordinance but the Court ruled that it was too late in this particular case and the Plaintiff prevailed--basically because the ordinance was previously incorrect at the time of the Plaintiff's suit. My attorney has stated that the court in this case did not rule all rental inspections unconstitutional--rather, just the way in which Flint was doing them. (FYI: I'm not an attorney, and I'm not giving legal advice--just passing along information.)
Good news: RPOA of Michigan promoted a bill to change Michigan's law regarding inspections. This law was signed by the Governor and goes into effect at the end of February 2018. In short, under the current law, municipalities are allowed to enter a rental unit without permission--IF there is a clause in the lease allowing the landlord entry. In other words, municipalities are allowed to enter under the landlord's contracted right of entry. This law is unconstitutional because it does not provide the tenant an opportunity to directly deny entry for a government rental inspection. These types of clauses in leases do not specifically give the municipality the right to enter--just the landlord. Starting in February under the new law, municipalities must get permission from the tenant to enter the premises for a rental inspection. The landlord must make a good faith effort to obtain the tenant's permission for the inspection. If the tenant refuses, the municipality must either get an administrative warrant or wait until the unit is vacant.