As noted in the ruling, they are prohibited from ruling on exclusively Parliamentary matters, both by the Bill of Rights 1688 (Parliament of England and Wales):

As noted in the ruling, they are prohibited from ruling on exclusively Parliamentary matters, both by the Bill of Rights 1688 (Parliament of England and Wales): > That the Freedome of Speech and Debates or Proceedings in Parlyament ought not to be impeached or questioned in any Court or Place out of Parlyament. And Claim of Right 1689 (Parliament of Scotland): > That for redress of all greivances and for the amending strenthneing and preserveing of the lawes Parliaments ought to be frequently called and allowed to sit and the freedom of speech and debate secured to the members. Whilst the Court determines the scope of Parliamentary privilege (i.e. determining what constitutes a proceeding of Parliament), there is a very clear reason they would not extend their purview to Parliamentary matters, and clearly they have no power to overrule Acts of Parliament.