Its so 'yesterday' to just an all bikes and quads. So brain dead, retarded and Mugabe-like.
t's pretty easy to ban Kwats and MX bikes without falling into the trap you caution against.
Simply outlaw non-street legal machines on the premises.
LS, as easy as that, problem solved. A noisy exhaust is an illegal bike - thats how they can police it. A HP2 making kak can be policed via the entry rules on a board (it in any case only 0.214563%) of bikers/visitors.
I don't like the Gestapo-like 'phone Erika - depending on the state of her PMS she'll decide the outcome of your trip' - idea. Make the rules simple and concise - only street-legal bikes (implying street-legal zorsts). We have to decide then - either a mean sounding performance zorst or access to Nature Reserves - easy as that. We must get these monkeys away from decision-making.
I know a lot of stupid people are f@king up our nature reserves and sensitive areas, but these Nature Reserve people sometimes act if they own the planet with all its fauna and flora. If 1% of people are dose - you don't have to act like a drill sergeant for the other 99%?
In order to keep out 99.9% of the culprits on their quads and MX bikes (which will be simple to regulate as mentioned above), they run the risk of alienating a lot of right-minded riders supporting their course.
I don't like this 'ask Erika' uber alles fuhrer mentality - rather use intelligent, transparent rules to govern access.
MHO - Hein