Yokohama Mayor Hiroshi Nakada decided Friday to allow his constituents to choose whether their personal data can be entered into the forthcoming national resident registry network.
The decision reflects his belief that municipal administrators cannot decide whether to participate in the network without consulting with residents, according to city officials.
Nakada will provide the national government with personal data on people who choose to take part in the network, which will go into effect Monday, they said.
Later Friday, the Public Management, Home Affairs, Posts and Telecommunications Ministry said it has determined that Yokohama's policy violates the Law of the Basic Resident Registers.
Yokohama is the largest municipality in Japan, with a population of some 3.45 million, and it is likely that many residents will choose not to have their data registered in the network.
Earlier in the day, Nobuo Hoshino, mayor of Kokubunji, western Tokyo, told a municipal assembly meeting that the city will not participate in the network until more sophisticated legislation to protect personal information is in place.
The move by Kokubunji and the possible abstention of many Yokohama residents will make the network incomplete, analysts said.
The system will link basic residency registries across Japan by matching information about people, including name, address, date of birth and gender, to an 11-digit individual number.