The court must decide if the deputy speaker of the assembly violated the constitution by refusing to allow a no-confidence vote against Khan at the weekend.
The move allowed Khan to get the presidency -- a largely ceremonial role taken by a loyalist -- to dissolve parliament and order an election, which must be held within 90 days.
Had the vote taken place, Khan was certain to have been booted from office.
President Arif Alvi upped the ante Tuesday by issuing a letter to the opposition saying if they didn't nominate a candidate for interim prime minister, the process would continue without them.
Khan has already nominated former chief justice Gulzar Ahmad for the role.
Pakistan has been wracked by political crisis for much of its 75-year existence, and no prime minister has ever seen out a full term.
There had been high hopes for Khan when he was elected in 2018 on a promise of sweeping away decades of entrenched corruption and cronyism, but he has struggled to maintain support with soaring inflation, a feeble rupee and crippling debt.
The opposition had expected to take power on Sunday after mustering enough support to oust him, but the deputy speaker refused to allow the vote to proceed because of alleged "foreign interference".
Khan said the opposition had gone too far by colluding with the United States for "regime change".
The cricket star-turned-politician says Western powers want him removed because he won't stand with them against Russia and China, and the issue is sure to ignite any forthcoming election.
Washington has denied any interference.
It is unclear when the court will rule on the issue -- or if Khan would even accept its decision -- but there is precedent.
In 1988, Muhammad Khan Junejo appealed to the supreme court after the assembly was dissolved by then-president General Zia-ul-Haq, who had taken power in a military coup years earlier.
The court agreed his government had been dissolved unconstitutionally, but ruled that since elections had been announced anyway it was best to move on.
In 1993, it ruled president Ghulam Ishaq Khan had also illegally dissolved the assembly, then with Nawaz Sharif as prime minister.
Although the government resumed business, it lasted less than two months before being dissolved again.
The supreme court is ostensibly independent, but rights activists say previous benches have been used by civilian and military administrations to do their bidding throughout Pakistan's history.
The military appears to be keeping out of the current fray, but there have been four coups -- and at least as many unsuccessful ones -- since independence in 1947, and the country has spent more than three decades under army rule.
