Fundamental principle idea, doctrine: conventional, legal, quasi-legal aspects.
Purpose: Separation of Powers explains the distribution of power but is largely power-limiting.
The control of power depends on its fragmentation (Harlow).
Classical view: 3 government functions : legislative, executive – administrative, judicial.
Separation of Powers may be approached as descriptive or as prescriptive (it requires).
Constitutional theory: no single doctrine or model, but many (vile); for example:
Separation of Persons: Constitution forbids different branches to consist of the same people (prevent over-concentration of power) (Montesqui; Locke).
Isolationist or non-participation model: constitution assigns one function to one institution and forbids interference by others in its exercise. E.g. Vertical: Roman Catholic Church – Canon Law: three hierarchys (power confined).
Participation of control model: checks and balances: institutions in different branches are empowered to control exercise of power by bodies in other branches (e.g. Horizontal: US constitution: congress, president supreme court); Marshall suggests this is the most sophisticated of the SOP models.
Constitutional practice in the UK debate amongst theorists (e.g. DeSmith v Munro).
Separation of persons: Composition laws illustrate this in its prescriptive form e.g. House of Commons Disqualifications Act 1975: e.g. Judges civil servants barred from membership of HC as legislature (compare e.g. Monarch : fusion).
Isolationist Model: (a) authorisation to tax assigned to legislature (parliamentary statute authorises executive to levy), executive cannot levy without statutory authority (Wiltshire Diaries); (b) parliamentary sovereignty; law – making (by statute) assigned to parliament, courts cannot dis apply statute. (Diplock in Duport); (c ) Royal Prerogative (mainly executive functions courts cannot question exercise (classical idea); but, at the same time e.g.: executive may be empowered by parliamentary statute to make secondary legislation.
Control Model: e.g. Royal prerogative: executive act of dissolution of legislature Parliament administrative law: judicial review of executive action; but the judges are the legislators of the common law (Munro: e.g. Shaw, Knuller) (exceptions to isolationist model represent illustrations of the control model).
Case study: illustrates the difficulties in identifying which SP model operates in UK.
Haughton v Smith (1975) HL refuses to recognise attempting the impossible as criminal (to do so would unsurp Parliament law-making: Hail sham): isolationist.
Law Commission (1980) (executive) recommends change in law (new crime) and reversal of the decision in Haughton v Smith.
Criminal Attempts Act 1981, s.1: person is guilty of attempt to commit an offence 'even though facts are such that commission of it is impossible.'
Anderton v Ryan (1985) HL: Parliament failed to create a new offence (asinine if guilty only when there is mens rea; dissenting judge (edmund David): new offence created; majority employs control model (and frustrates Parliament).
Shivpuri (1987): HL reverses Ryan decision by invoking 1966 practice direction (i.e. Reassertion of isolationist approach).
“The difficulties with the doctrine arise mainly if an attempt is made to regard it as absolute. Certainly the doctrine continues to shape constitutional arrangements, and [it] influences decisions, and in some limited form is necessary both for efficiency and liberty.” (Munro).