Ultra vires is a standard legal term which means in excess of power. It is about what officials are not allowed to do. For example the ministers in Her Majesty's Government are all sworn of the Privy Council. They swear an Oath of loyal service. It is one they treat with contemptuous indifference. Granting power over England & the rest of the EU means they did not assist and defend all civil and temporal Jurisdictions, Pre-eminences, and Authorities, granted to Her Majesty .... against all Foreign Princes, Persons, Prelates, States, or Potentates. In fine they act ultra vires; they are Traitors. See Treason At Maastricht for more and better details.
Ultra Vires ex Wiki
Ultra vires is a Latin phrase meaning literally "beyond the powers", although its standard legal translation and substitute is "beyond power". If an act requires legal authority and it is done with such authority, it is characterised in law as intra vires (literally "within the powers"; standard legal translation and substitute, "within power"). If it is done without such authority, it is ultra vires. Acts that are intra vires may equivalently be termed "valid" and those that are ultra vires "invalid".
That is clear enough. The Wiki has more on the applications.