Shamima Begum ran away to Syria as a 15-year-old to join the self-proclaimed Islamic State. But when the terror group was defeated, she ended up in a refugee camp in Syria.
Now, she wants to return home to the UK, but her British citizenship has been revoked by the government who say she poses a threat to national security.
The Supreme Court is deciding exactly how her case should be handled, and its decision could have huge implications on how cases like Shamima’s are dealt with in the future.
Home affairs correspondent Dominic Casciani explains.
Filmed and edited by Alex Dackevych