|Warning wws - No references to firearms in the following comments.... may contain boring bullshit
self regulation means a bit (and sometimes a bit more) of thinking about what you do before you do it, with the thinking being about what the impacts will be, and modifying behavior as a result. I reckon it's worked well for climbing in Australia - it's mostly unregulated and despite Reluctant's fears may continue to be so for a while to come. I think it's the case because the combined impact of all this "unregulated" behaviour, from bottom feeders like myself to crag developers is mostly below the threshold of alarm of any authority, e.g. Not enough to worry about.
Self regulation works when most people are aware, at some level, that increasing regulation WILL be imposed if their impact is too great. Burying your turds,keeping groups small, carrying out track care, climbing logs to avoid vegetation, not taking your dog to a NP are all examples of how climbers mitigate their impact on the environment. Others can see this and hopefully think we're doing enough. We're lucky in that our favorite medium, rock, is pretty tough.
Self regulation does not necessarily mean consensus - we can argue about the subtilties of bolting forever, but works well when it involves respect of others efforts - e.g. Be it by not retrobolting passport to insanity or top roping thru the rings.
Lastly, self regulation involves not hurting yourself so badly you need others help, especially expensive rescues. Fortunately, I've found climbing scares me more often than hurts me.
Hope that helps.
Involvement of a "community"', representative body or government is external regulation - you have to obey other rules than your own. Climbers still have to do this when engaged in related outdoor activities like camping or four wheel driving.