Unless the property is in your name alone, best that you consult with a lawyer first, but definitely get them out of there ASAP.
I don't know the laws regarding squatter's rights in your state, but if they live there past a certain amount of time with no legal action, then you're REALLY in for a fight.
My suggestion is that if you're able, buy your BIL out, which will make removing them that much easier. Even if you just buy the half for $1 and change the name to yours alone and agree to pay your BIL "rent" until his half is paid, it beats going up there guns blazing.
Just because you CAN do something, doesn't mean you SHOULD.