If it is AT ALL on your property, you can require them to move it at their expense: if they will not do so voluntarily, you could file a legal action seeking a court order requiring them to do so. They have no right to build, etc. on your land.If it's on their side of the line, they can put it as close to the line as they like as a general matter (it is their property; they can do, build, locate, etc. what they want, where they want, on it), subject to any local municipal (town or city) laws (code) about any required "set back" from adjacent property. Go to the municipal clerk's office and check on the code in this regard: whether a certain distance or space is required and, if so, how much. If there is a restriction in the code and the violate, contact the building department to enforce it.