Challengers, led by investment manager Gina Miller and backed by the Scottish government and others, say May must first get lawmakers' approval as leaving the EU will strip Britons of rights they were granted by parliament. That view was backed by London's High Court, prompting the government to appeal to the Supreme Court, the highest judicial body in the land. The case has attracted huge attention from markets, with investors hoping parliament will temper moves towards a "hard Brexit", and it has again brought to the fore some of the ugly divisions among Britons produced by last June's referendum.
In the US session, tomorrow, Existing Home Sales figures will be released. Decline to 5.54 million is anticipated.
Figures to watch:
EU Membership Court Ruling (Tuesday 10:30)
Existing Home Sales (Tuesday 16:00)