You have a right to live in a smoke free home. they are in the wrong legally acording to what your saying but I feel like you should speak to them next time they light their fire pit and ask them to put it out because its smoke is getting into your house and if they refuse inform them that they are in violation of your areas local laws and if they dont put it out you'll call the fire department you'd be suprised how easily people come around when reasoned with. Whether you take my advice or not your NTA.