The militants, who had used mobile courts, told the BBC the Mohmand district has been divided into four judicial zones, each with two judges and a permanent court address.
The BBC report said the militants control large areas of Pakistan's Federally Administered Tribal Areas bordering Afghanistan.
"There will be eight judges, two for each zonal court, and there will be a top judge to whom appeals can be made," a spokesman for the Mohmand Taliban told the British network, which said a tribal administration official confirmed the courts are functioning.
A spokesman for the Pakistani Taliban Movement said permanent courts also are in operation in Bajaur district, north of Mohmand.
In an example of Taliban justice, its militants killed a couple last March after a Mohmand Taliban court found the two guilty of adultery, the BBC said.
Taliban insurgency has shot up in the areas despite a prolonged military campaign to re-establish its authority.
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