In this first paper, Margit Cohn will provide a broad perspective for the panel by considering UK prerogative powers, argued in Miller and elsewhere, in light of comparative law and the looser concept of “non-statutory” powers, sometimes considered in the UK as “third source” or “new prerogatives”. The questions addressed in the panel will be reconsidered in the context of US and Israeli law (with some references to France). Are NSPs equivalent to prerogative powers in other systems? How are NSPs recognized and treated? How does the residuality principle apply and what is the relationship between statute and NSP? Are there constraints on the invocation of NSPs when interfering with individual rights? And would Miller have been decided differently in other systems?