The case marks a rare confrontation between the prime minister, the courts, and Parliament over their rights and responsibilities, and also involves Queen Elizabeth II.
Britain's highest court says it will announce the decision at 10:30 a.m. after holding three days of hearings last week before 11 judges. The government's opponents argue that Johnson illegally shut down Parliament just weeks before the country is due to leave the 28-nation bloc for the "improper purpose" of dodging lawmakers' scrutiny of his Brexit plans.
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