Unique tenant situation

[Mitchell Welle]

Hello, this is my first time posting a discussion and I am what you might call a manager in training. I am located in the Fargo/Moorhead area and the property in question is in Fargo, so North Dakota laws and procedures would apply to this situation. Almost a month ago a tenant was given a pay or vacate notice and he chose to vacate so he was not evicted. However, another tenant is now allowing him to stay at his place and has moved the few furniture items (bed, recliner, lamp, etc) he has into the other tenant’s unit. The lease does not specify a time length for when a guest becomes a resident, only that all tenants must be approved by management. Is there any way I cant proceed with removing the delinquent ex-tenant and not the one who he has moved in with? Thank you’