 So, in "R v Secretary of State for the Home Department, ex parte Khawaja" [1984] AC 74, the House of Lords held that the question as to whether the applicants were "illegal immigrants" was a question of fact that had to be positively proved by the Home Secretary before he could use the power to expel them.The power depended on them being "illegal immigrants" and any error in relation to that fact took the Home Secretary outside his jurisdiction to expel them.However, where a term to be evaluated by the authority is so broad and vague that reasonable people may reasonably disagree about its meaning, it is generally for the authority to evaluate its meaning.