In Britain, Parliament makes the laws, Ministers and civil servants [collectively the Government] implement them – and the Judiciary judges whether laws have been followed.
That includes whether Parliament has not broken in any other laws in making new ones, and whether the Government has implemented the laws without breaking any other laws. In either case, if yes, which should prevail must be determined. That process is called Judicial Review.
Andrew Holland, supported by Backlash, has instigated such an action regarding the CJIA, the “Extreme Porn” law.
Further reading here