The Barclay Brothers bought the island of Brecqhou in 1993 for £2.3M and since then have fortified the island with a gothic castle. Since 1993 they have been agitating to have Brecqhou seperated from neighbouring Sark which the Seigneur of Sark, a Mr. Beaumount, is formerly the feudal Lord. Sark and Brecqhou fall under the legal auspices of the Bailiwick of Jersey, the governor of which is appointed by the Duchess of Normandy i.e. HM the Queen.
Visits to the island are forbidden by the Barclay Brothers as it is their private property. However, due to their deliberate flouting of the Laws of Sark (driving cars, etc) and considering they have recently made 20% of the population of Sark redundant they have made many enemies in the Chief Pleas or Parliament of Sark.
If someone was to trespass on Brecqhou the owners of the island would have to appeal to Seneschal of the Chief Pleas, the elected leader of the parliament. He would be unlikely to prosecute anyone who had upset the Barclay Brothers considering their behaviour. Furthermore, technically the owners of Brecqhou would have to request that the Constable of Sark come to their island and physically remove any squatters and this action would require approval by the Seigneur.
Visitors to Brecqhou would need a boat, parachute or hang-glider as the island can only be accessed by sea or air.