The former cricket star had moved to break up the lower chamber ahead of a no-confidence vote against him that he had looked destined to lose. When opposition parties united against Khan last week to push for the no-confidence motion, the deputy speaker of parliament, a member of Khan's party, threw out the motion, ruling it was part of a foreign conspiracy and unconstitutional. Khan then dissolved parliament.
The court has said in its judgment that the vote should now go ahead. Thursday's ruling in the capital Islamabad could spell the premature end of Khan's tenure in a country where no elected leader has finished their full term in office.
The constitutional crisis has threatened economic and social stability in the nuclear-armed nation of 220 million people, with the rupee currency hitting all-time lows earlier on Thursday and foreign exchange reserves tumbling. He is set to address the nation on Friday (April 8).
The 69-year-old, who steered Pakistan to cricket World Cup victory in 1992, came to power in 2018 after rallying the country behind his vision of a corruption-free, prosperous nation respected on the world stage.
But the firebrand nationalist's fame and charisma may not be enough to keep him in power. He could not deliver on all of his lofty promises and failed to avert an economic decline partly sparked by the COVID-19 pandemic.
The opposition has said it wants early elections, but only after delivering a political defeat to Khan and passing legislation it says is required to ensure the next polls are free and fair. Pakistan's election commission said on Thursday the earliest it could hold the ballot was October.