“[94] … a rule is any requirement which a migrant must satisfy as a condition of being given leave to enter or leave to remain, as well as any provision “as to the period for which leave is to be given and the conditions to be attached in different circumstances” (there can be no doubt about the latter since it is expressly provided for in section 3(2)) [of theImmigration Act 1971 ]. I would exclude from the definition any procedural requirements which do not have to be satisfied as a condition of the grant of leave to enter or remain. But it seems to me that any requirement which, if not satisfied by the migrant, will lead to an application for leave to enter or remain being refused is a rule within the meaning of section 3(2). …………………………… [96] It seems to me that this approach best reflects what Parliament must be taken to have intended when it enacted section 3(2). There is no evidence that it would be unduly burdensome, let alone administratively unworkable for the Secretary of State. It causes her no administrative difficulty to make the most detailed rules and then lay them before Parliament. I acknowledge the burdens that would be imposed on the Scrutiny Committee to which Lord Hope refers at para 65. It is, however, a striking fact that the immigration rules are already hugely cumbersome. The complexity of the machinery for immigration control has (rightly) been the subject of frequent criticism and in urgent need of attention. But it is not relevant to the present issue. [97] If the boundary is drawn where I have suggested, that should introduce a degree of certainty which ought to reduce the scope for legal challenges. The key requirement is that the immigration rules should include all those provisions which set out criteria which are or may be determinative of the application for leave to enter or remain.”