Civil servants at GCHQ were barred from joining unions by an order of the minister, exercised under the royal prerogative to sack or change the terms of employment at will. This occurred without consultation because that would have led to union attempts to disrupt GCHQ and harm “national security”. HL said that both prerogative AND executive action derived from statute had to conform to laws of judicial review (Lord Diplock) and were justiciable, which would ordinarily mean procedural propriety has to apply (i.e. in a normal case the union would win). However an exception was carved out where national security was concerned, (the HL saying that national security is a matter to be judged exclusively by the executive, since some evidence would damage security if shown in a public court), and so the judicial review rule of “procedural propriety” did not apply. Lord Scarman particularly emphasised the national security point. In the past judicial review had been confined to saying whether a prerogative exists and what were its limits. In this case HL asserted the right to review the manner in which a prerogative was exercise (Paul Craig).