Estoppel and public law duties

In Asaad v Minister for Home Affairs (No 2) [2019] FCAFC 214 the Full Court explained the interaction of estoppel and public law duties.

Care however must be taken to not interpret the Court’s observations as laying down a blanket rule that it will always be lawful for a Minister to revisit the exercise of a discretion. For example, when it is the re-exercise of the discretion in relation to the same set of facts, it may be that the subsequent exercise is unlawful as an abuse of process, or an exercise of the duty for an improper purpose, or otherwise invalid because of bad faith. Assad does not preclude these conclusions in the appropriate scenario.