If I were a lender, no offense, you would probably be the worst market for me and I would likely not give you another loan.

Lease expressly prohibits criminal activity at the property, but doesn't really cover this detail.

Smokers have a hard time understanding how offensive smoke smell is to non smokers.

However, you also don't want to take the liability of housing people engaged in criminal activity. 

I would also recommend doing a more comprehensive screening of your future applicants (criminal, credit and eviction history) and getting previous landlord references so that you can avoid this situation in the future. 

Threats of criminal enforcement, etc.Introduce them because you want to help, but you're not in a legally strong position to collect fees.

Class 3 offenses are the least serious type of misdemeanor crime, but if they are a repeat offender they may not be answering the phone because they are busy for up to 20 days over at the Wake County Detention Center.

If you can prove intentional damage was inflicted to your property, you can file a criminal complaint with the local police.

That's just one example of what Mike means...there are plenty, plenty more where that came from...that was just the first and most criminal example to come to mind, as it involved about $5T and about 7000 lives.

(Singapore makes this even easier with an automatic visa on arrival - unless you are a criminal.)