Commission Regulation (EC) No 262/2009 of 30 March 2009 laying down requirements for the coordinated allocation and use of Mode S interrogator codes for the single European sky (Text with EEA relevance)
Article 6U.K.Associated procedures for air traffic service providers
Air traffic service providers shall not use data from Mode S interrogators operating under the responsibility of a third country if the interrogator code allocation has not been coordinated.