Despite opposition to the Marine Offences Bill both in Parliament and (belatedly) from campaign groups the legislation was passed and came into force on 15th August 1967.
The fort-based stations (BBMS, Radio City and Radio 390) had already been closed as the result of successful prosecutions under the Wireless Telegraphy Act 1949. Although in the case of Radio 390 the station had managed to stay on the air until 28th July due to a series of appeals against their prosecution.
The ship-based stations were the ones directly affected by the introduction of the Marine etc Broadcasting (Offences) Act. Despite early announcements of defiance all but one of the ship-based stations closed ahead of the Act’s implementation.
Radio 227 closed on 23rd July 1967 and Radio 355 closed on 6th August 1967 - ahead of the introduction of the MOA because of insurance renewal issues with their ship, the Laissez Faire.
Radio London, despite earlier claims that it would continue in defiance of the new Act, closed at 3.00pm on 14th August 1967.
Radio 270 had always said that it would not contravene the new legislation and closed at midnight on 14th August 1967.
Similarly Radio Scotland did not wish to challenge the new legislation and closed at midnight on 14th August 1967.
The only station to defy the introduction of the MOA was Radio Caroline and both its stations continued to broadcast after the introduction of the MOA., Now using the call sigh Caroline International. Caroline South made a statement of defiance at midnight on 14th August when British DJs Robbie Dale and Johnnie Walker continued broadcasting.
Radio Caroline North was in a slightly different situation due to the constitutional crisis which had developed with the Isle of Man .although the station adopted the call sign Caroline International at midnight on 14th August (in common with its sister station in the south) technically the MOA did not apply to the Isle of Man until 1st September 1967.
At midnight on 31st August 1967 (when the MOA became effective in the Isle of Man) Caroline North also continued broadcasting in defiance of the new legislation.
The British Government published this advertisement in newspapers (both in Britain and abroad) to try and discourage anyone from assisting an offshore radio station after the MOA became effective on 15th August 1967.