The decision could have significant implications not just for immigration and asylum policy, but also for the future direction of Rishi Sunak's government, and the Conservative party more widely.
Here is what could follow from a government win or loss:
Government wins the case
While only the five law lords hearing the case will know for sure before their decision is made public at 10am on Wednesday, there is speculation that the relatively rapid process - a ruling was seen as more likely in December - could signal rejection of the government's arguments, endorsing the court of appeal's decision in June.
Paradoxically, a loss is seen by some inside No 10 as not just likely but in some ways welcome.
If the highest court in the land gives the green light to the deportation scheme, Sunak and Suella Braverman will have to enact a policy that many critics viewed as largely performative and unlikely to achieve its one stated aim: to significantly reduce the number of people arriving unofficially in the UK on small boats.
Nearly 46,000 people made this Channel trip last year, and while numbers are down so far in 2023, they remain way above the number that could be flown to Rwanda.
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