The Supreme Court was very clear on these clauses: We determine that because the lease includes a provision in violation of § ATCP 134.08(3), the landlord, Baierl, may not enforce the lease against the tenants.

., but again enforcement may be after the fact.  

My only thing is why they didn’t enforce a renewal option on their contract.

I'm concerned with how to enforce any rules now that he's trying to skirt the lease.

Whereas in the past lenders did not attempt to enforce the “due on sale” clause, this was in an era when interest rates were heading lower and transfers of ownership were not easy to identify.  

Regardless of who wrote the lease, if it violates state law it is not enforceable.

If the lender does find out that a property transfer has taken place, and chooses to enforce the due on sale clause, the lender must provide the seller (debtor) and, if applicable to state law, buyer with notification of default under the mortgage or deed of trust, and specific time as specified by state law to cure the default.  

If they are VERY professional, they will have their processes in writing as verification that policies are enforced equally and fairly by their entire staff.6.

My only thing is why they didn’t enforce a renewal option on their contract.

After operating 1 rental for 2 years and another for just a few months, I just got notification from the code enforcement at my municipality (whom I had visited in person) that I didn't file a paper correctly and fines are possible.