Urgent help needed

Rent Arrears

Hi we are managing one property where we let that property to a couple with a kid in october 2013 now we find out that the girl and kid moved out and the man in the property brought in another guy who is drug dealer and the have big dog inside the flat ( we received lots of complaint from other tenants in the building ). (as per agreement they cant have any pet at the property). when we approached the tenant and told him and inquire about various incidents he stopped the rent and now saying, do what ever we can he is not leaving unless he gets the court order. please advise