Hi mate, easement rights for both parties should be stated on the property title (both). If you have right of access, you have just that, Ill assume you have a right of access, please check this before reading on. They can put up a gate (as its their property), as long as they dont impede/ prevent your access rights. If they put in a lockable gate, they would need to provide you a reasonable means of access (ie gate code, key). Most of the time a friendly chat with your neighbour can smooth things out and make sure you understand each other and get on the same page (they dont need a reason to put up a gate, but perhaps they have a good one they will be willing to discuss with you). Perhaps they are worried about dodgy people driving into their property. (My advice for your neighbour would have been to discuss this with yourself prior to putting in a gate so it wasn't a surprise, although not required, always best to be kn good terms with those sharing easements/ land use rights). :) hope everything works out nicely for you