Clearly if you want all your own decisions made you need to move to a place that is completely your own.
I imagine the reason you are living there is because since it is your dad's it is quite cheap.
The situation benefits you, and it benefits the other individual also living on the property that you do not like.
You seem to be looking for advice to keep the benefits of the situation, but changing the living situation to your own terms without yourself being the property owner.
The dad is helping you, and is helping someone you do not want him to help with his own property. You have decided you wish to pick and choose how another man uses his property even when it is being done to your benefit.
I honestly can't see anything good coming from that attitude, and would advise you to move as well. Of course then you will have less for the same money, but you can choose how what is yours is used.
What about the sewer hook-up? Does the camper have a sewer hook-up? If not, is that in compliance with zoning and sanitation laws? I'd look into that, too. If you make it as difficult as possible for the doper, maybe he'll move out.
Such violations if there is any would fine the property owner, in this case the dad who is letting everyone live on his property.
Personaly if I was the dad and he complained resulting in fines for me I would boot him out, not the brother. Or I may just rent the brother if they were unable to live in the camper because of the resulting complaints a room in the house and let the ungrateful complainer deal with that.
If either of them had a problem with it they could leave the financialy beneficial situation and get thier own place.
I can understand not wanting criminals around, and if they actualy are involved in drugs it will bring around a bad crowd, the type of crowd likely to burglarize or rob you if they get desperate.
I would not want them living there either, and would talk to the property owner about it.
If they are using your electricty as you say there is things you can buy that record the amount of electricity being used on various lines. Purchase one, and charge them for the electricty they use, and a percentage of any other utilities you pay for that they use like water etc.
They should pay thier share.
If having to pay thier fare share causes them to move, then the issue is resolved.
That is assuming it is you paying for the utilities and not the property owner allowing them to stay there.
If you want to decide how the property is used, get your own. Trying to find legal hassles you can create to choose how another man's property is used seems rather ungrateful.
I am all for talking to the owner and trying to change things using logical discussion. Trying to strong arm the property owner and looking for legal issues to get your way against the will of the person helping you with thier land just seems really ungrateful.
I wouldn't let someone with that mindset live on my land.