Dave Moorhouse, 56, of Huddersfield, England, said his Jack Russell terrier, Rocky, was stolen in January 2007 and the microchip provider, Anibase, refused to pass on the pet's new address, claiming it would violate the Data Protection Act, The Daily Telegraph reported Thursday.
Moorhouse said Anibase contacted him in April after the new owners apparently tried to add their information to the microchip.
Moorhouse said he contacted police but was told the information could not be passed on because they could find no criminal action to prosecute and a Huddersfield County Court judge ruled the matter was out of his jurisdiction.
"What's the point of having your pet microchipped if you can't get him back?" Moorhouse said.
Steven Wildridge, managing director of Animalcare, which operates Anibase, said keeping the information private is "an obligation under the Data Protection Act. If the individuals involved do not want us to pass on their details to the original owner then we cannot do so unless compelled to following a criminal or civil proceeding."