Hello and thank you for the opportunity to assist you. My name is ***** ***** I will do my very best to answer your legal questions.
First and foremost, obviously it would be great if you could simply talk to the neighbor and inform him of the bylaw which requires that he not obstruct your view. That may take care of the problem. However, if you can't get through to the neighbor, or the neighbor refuses to do anything after speak to him, then I would complain to the HOA and see if the HOA will do anything about the neighbor ignoring the bylaws.
If the HOA does nothing, then you do have the right to sue the neighbor yourself to enforce the bylaws. Of course, you'd have to pay your attorney's fees out of pocket. Unfortunately, it is unlikely that you would get an award of those attorney's fees in court.
Finally, you have the right to cut the tree branches back to the property line yourself. This is the common law rule in the absence of the bylaws that you mentioned which puts the burden on the neighbor. This may be the better alternative than suing if the neighbor refuses to voluntarily fix the problem, and the HOA does nothing.
Does that answer your question? Please let me know if you need clarification, as I am happy to continue helping you until you are satisfied.