... The English language evening broadcasts from Radio Luxembourg were intentionally beamed toward the British Isles by Luxembourg licensed transmitters, while the intended audience in the United Kingdom originally listened to their radio sets by permission of a Wireless License issued by the British General Post Office (GPO). However, under terms of that Wireless License, it was an offense under the Wireless Telegraphy Act to listen to unauthorized broadcasts such as those transmitted by Radio Luxembourg. Therefore as far as the British authorities were concerned, Radio Luxembourg was a "pirate radio station" and British listeners to the station were breaking the law....
...the new Postmaster General Edward Short immediately pushed through legislation making it illegal for British citizens and companies to work for, supply, or advertise on an offshore radio station. While the bill was going through parliament, the Post Office summonsed all the fort based stations for broadcasting without a licence. The authorities now decided to use the powers gained in 1964 putting the forts within territorial waters. After long court battles all the stations were forced to close. Two forts remained in international waters, and one of these became the place of violent battles, as two stations vied for control. The other was blown up by the British Army in 1967.
The new anti pirate legislation became law on August 15th 1967, and all the stations except Radio Caroline closed down, knowing they could not survive financailly. On the Isle of Man, the Manx government tried to avoid the new law being imposed by Westminster, and a bitter battle ensued. They were forced to ratify the law which came into effect on the Isle of Man two weeks after the mainland.