He/she is just camping next to the drug house for at least a few hours so we couldnt sell our drugs, isnt there a limit of time you can camp next to the drug house? Anyways that's not cool.
Cops are able to camp wherever they want for however long they desire. There is no rule implemented to stop this because there are many, many different ways into the drug houses.
You can wait for the cops to go offline and then sell your drugs then. Else, you face the risk of being arrested.