Well it sounds like your legal system is non-existent if there have been laws passed to evict these people but it never happens.
Force rules the day when there is no such thing as a legal system or government that can bring justice for the civilians.
If there is no legal system then power and force is what is going to be the only factor in who controls territory and resources. Basically you either need a larger army (in numbers and resources) if you want to go head to head, or you need to resort to a guerilla campaign (like the french resistance of WWII, or the norway raiders in WWII). Cut off their resources, make their transportation and communication become non-existent. Put up IED's leading into and out of their main encampments.
You could go "in between" the two "force" routes I suggested and have special ops type missions in which you use surprise and overwhelming fire suppression to attack a critical object, but don't get into a full blown fire fight.
I'd recommend giving this book a read before you try any special ops or guerrila operations (it's really just a good read in general):
http://www.amazon.com/SOG-Secret-Americas-Commandos-Vietnam/dp/0451195086