Kenya's High Court stopped the telecoms regulator on Thursday from monitoring mobile phone networks to detect counterfeits, saying the regulator had flouted the constitution and failed to involve the public when it rolled out the plan.
Operators including market leader Safaricom strongly objected to the plan when it was made public last year, saying it would give the regulator access to other customer data including calls, messages and financial transactions.
A private citizen challenged the regulator's decision in court in a case in which the operators were enjoined as interested parties and the judge, John Mativo, ruled against the regulator in a judgment delivered on Thursday.
There was no immediate reaction from the operators or the regulator, the Communications Authority of Kenya (CA).
CA said in February last year it would install equipment in the networks of the country's three mobile operators, to improve its monitoring of counterfeit mobiles, in line with its consumer protection mandate.
Poorly made counterfeit phones, imported mainly from Asia, are prevalent in many African nations and regulators say they are widely used by criminals as they are difficult to track.
The regulator, which has switched off counterfeit mobiles in the past, says consumers are still exposed to such devices, justifying the monitoring system.
