How can the legislature force the executive to do something? Benn Act/Surrender Bill Watch
If you've studied law, you should have come across statutes prescribing positive obligations on, amongst others, statutory bodies and Ministers. This is nothing new. In any event, duly passed Acts of Parliament are the supreme law of the land and cannot be called into question in any court, including the Supreme Court. This is taught in the very first lesson of law school. Unless you had studied law overseas, you really shouldn't be asking this question.
Arguably, the Crown - and by which, I mean the executive - could have blocked the legislation by refusing Royal Assent. But obviously that's not been done in three centuries. Although Queen's Consent, where a Bill requires the authorisation of the Crown to proceed when it deals with issues of the Royal Prerogative, has been refused in recent times.