Rather than getting tied down in the actual messy pragmatic details of reality, I am going to try and consider what you might want from an access scheme. How you actually achieve whichever of these you decide you want is left as an exercise to the reader... :read:
I'm going to start from the assumption that these decisions are being made by a body which has absolute control over the cave (they can give access to anyone or no one as they see fit).
Firstly, you need to decide a principle on which to decide access matters; I propose this could be either:
a) access should never be granted unless it is shown the access _should_ be granted, or
b) access should be granted unless it is shown the access _should not_ be granted.
Then there are various possible motivations for allowing or denying access. You may wish to restrict access:
1 ) for specific significant conservation reasons (delicate formations, bats, scientific interest etc, not just polish)
2 ) to prevent queuing/'too many people'
3 ) to prevent use commercial groups
4 ) to prevent use by the 'general public' (to allow only 'cavers' to use the cave)
5 ) to prevent use by the general caving population in such a way to give preference to your own club/group etc, either in return for managing access or as a reward for effort expended in the cave
6 ) to prevent use by less experienced cavers for non-conservation reasons, where that cave is suitable for novices
7 ) to prevent use by 'non-cavers' for safety reasons (dangerous entrance area)
8 ) to prevent use by, in general, anyone, for safety reasons that apply also to cavers (dangerous cave)
9 ) to prevent anti-social behaviour such as littering
10 ) to allow only your own organizations and other specific people to carry out a generally beneficial activity such as digging
I'm sure people can think of more...
I think access should generally be generally be granted unless it is shown that it shouldn't be (b), although I can see arguments for (a). I think everyone would agree on (1). I would only agree with (2) if a completely fair an equitable system was designed that didn't benefit, for example, people who were in clubs/knew the access people/were known in the caving community/were more experienced. (3) I am not sure about; provision should be made for both commercial and non-commercial activity. (4) I am not able to justify on its own - if there are safety considerations etc then that's different. I would hate to think that you can only be a 'caver' if you wear an oversuit, belong to a caving club and 'cave' in a prescribed fashion... (5) I would in general disagree with, but if that's what you want then at least state that openly. (6) I would also disagree with; if there is no objective reason not to have novices in a cave then I would argue everyone should have the same right of access regardless of experience (I can think of specific reasons though). (7) seems reasonable to a degree but things like the notices at the entrance to Porth yr Ogof (not actually been in the cave, just seen the 'you will die if you are not a caver!' signs) would be preferable to me than just a gate where possible. (8 ) needs to be treated with EXTREME caution, as in general people should be allowed to do risky but not excessively things (like cave!) but if the cave is a deathtrap and this is not obvious then some kind of restriction (even if again only a sign) seems reasonable. (9) is also a tricky one; I think there are sometimes existing laws and powers to deal with this? but sometimes some people do just go and ruin it for everyone else. (10) makes me concerned; I prefer to think that we all share rights and responsibilities for caves, and that while it is obviously rude (and therefore worse than illegal in Britain) to steal someone's dig, I don't like the idea that it is "XYZ's" cave.
To me 'open' access implies that a novice but keen and competent caver from a distant country who speaks no English should be able to read a (translated) description, rock up to the cave and get on with caving. If the guidebook 'tackle requirements' includes 'adjustable spanner' then that seems fair to me - it is easy for anyone to obtain, and it doesn't make any difference who you are or who you know.
PS As a side note it was a surprising, at first, how different caving access and climbing access are. In climbing a significant fraction of venues have 'unknown' legal status in terms of access (but have historically been fine). Some very popular venues are known to be technically trespassing but are basically OK-ed by the BMC because there has never/rarely been a problem, with the caveat 'if asked to leave do so. A photo of you climbing in front of the 'no climbing' sign at the popular Tirpentwys bolted sport crag (so about as obvious as British crags come) is de rigeur... There is a large section in the Rockfax Dorset guide (a high-quality professionally published guidebook) detailing the bits of climbing around Lulworth owned by an estate who do not allow climbing with the text on every page (paraphrasing) 'climbing is not allowed, this information is for completeness only! Outside of I think a single venue close to London, there are no climbing crags where climbers pay anything to climb. I assume the major difference in caving is that it is much harder to blow a crag up than just block up an entrance...