The government is challenging the court ruling. The outcome of the Supreme Court hearing will determine whether the Prime Minister (who is for these purposes "the government" ) has to get the agreement of parliament in order to trigger Brexit.

If the Supreme Court determines that under existing law she does not have that authority then parliament's approval has to be obtained. It would of course in theory be possible to introduce legislation that would change existing law, and give her that authority, but that would require parliamentary approval in itself.