Actually, if you look it up, you will find that regulated means something is governed or directed according to rules or laws. A well-regulated militia follows prescribed rules (not necessarily rules considered legal, but rules nonetheless.)

I must plead ignorance as to the contents of 2nd amendment, and who the OED is (are?) as I am from Cda and am only vaguely aware of what you are talking about.

If you look through back-copies of threads you will find many good links to on-line dictionaries. You will no longer be at a loss for the definition of words.