We all know that gliders and their pilots have an exemption from most laws - those of physics included... [[ ducks for cover ]]
But not the one on landing on an occupied runway without ATC permission. I raised it with the CAA once - pointing out that gliders don't have the option of going around in most cases and that compliance could result in riskier off airfield landings - but was firmly told there was no exemption and they would not consider one.
It's not such a big issue at gliding sites with large areas of grass and no marked runways - you cannot be guilty of landing on an occupied runway if there isn't one - in that case one should land keeping the other gliders on the left (in theory). With actual runways it can be a real issue and site rules may require you to land long enough to roll to the end so as to leave room for other gliders behind you. If the winch is parked at the upwind end of the runway it requires some precision to have enough energy reach the end of the runway but not overshoot into the winch. Thus violating one of the three most useless things in aviation rules - runway behind you.
If caught I would state 'correctly' that I had violated because it was an emergency. However, at one time (I don't know if it still applies) there was a requirement to notify the CAA in writing if you broke a rule for such a reason, which I don't - so they could get me anyway.