Khan was admitted as an advocate to the Supreme Court of Pakistan in 1991.[5]
In September 2000, Khan was appointed as a judge of the Peshawar High Court during the administration of Pervez Musharraf.[1] Notably, Khan declined to take the oath under the Provisional Constitutional Order on November 3, 2007, and did not accept the Naek formula.[1]
Khan was one of the judges reinstated on March 16, 2009, after the lawyers' movement, along with former Chief Justice Iftikhar Muhammad Chaudhry.[1] After serving as a Peshawar High Court judge for nine years, he was appointed Chief Justice of the Peshawar High Court in October 2009 and was elevated to the Supreme Court on November 17, 2011.[1] He authored many most important cases in the history of Pakistan including panama papers which led to the disqualification of the then Prime Minister Sharif in 2017 .