Neighbour does not park within own space

Our neighbour whose allocated parking space is next to ours has a vehicle which is quite large for our relatively small spots. He persistently parks over the front line of his space into and over common property, making it difficult for others to manoeuvre their cars in our small garage. Frequently he parks over the side border of his space intruding into ours. Sometimes he intrudes both into our space and common property. He believes that the problem is ours as we will not do as he suggests which is intrude into the space next to  ours on the other side. The space on the other sides is usually not occupied by a vehicle (though occasionally is) and we do not believe we have the right to use someone else’s space under any circumstances. What can we do to stop him from parking on common property and in our space?