The Flexibility Rule in Administrative Law

Administrative officials are permitted to have policies as to the exercise of their discretionary powers, but those policies must be flexible, not rigid. The “flexibility rule”, as I call it here, is nearly a century old. Over time, it has become part of the furniture of judicial review: often used, rarely examined. That neglect has led to confusion, on display most recently in R (Sandiford) v Secretary of State for Foreign and Commonwealth Affairs, in which the Supreme Court appeared to misunderstand key aspects of the flexibility rule. In this article I try to put the flexibility rule back on a sound footing. I argue, first, that the flexibility rule requires authorities to treat policies merely as rules of thumb. Second, the primary justification for the flexibility rule is neither legislative intent (as claimed in Sandiford), nor the avoidance of error (as commentators tend to assume); it is the value of participation. Third, and as a result, the flexibility rule ought to apply to policies governing the use of prerogative and other non-statutory powers (again contra Sandiford), as well as to policies governing the use of statutory powers.