5.7 The Separation of Powers

The doctrine of the separation of powers divides government between

groups with different interests or purposes so that no power centre can

act without the co-operation of others and each ‘checks and balances’

the others. Thus the separation of powers is a way of protecting the rule

of law. Article 16 of the Declaration of the Rights of Man (1789) states

that ‘a society where rights are not secured or the separation of powers

established has no constitution’. The separation of powers is associated

with the civic republican tradition the aim of which is to prevent domi-

nation by any single group (Chapter 1). For example the notion of law

would be meaningless if the lawmaker could interpret its own laws.

In the words of James Madison ‘The accumulation of all powers, legis-

lative, executive and judiciary, in the same hands, whether of one, a few

or many, and whether hereditary, self appointed, or elective, may justly

be pronounced the very definition of tyranny’ (The Federalist 4, 1987,

p. 303). Thus in England the competition between two branches of gov-

ernment, parliament and the king, was settled by war in the seventeenth

century while the third branch, the courts, stood on the sidelines.

In his most famous work The Republic, written in the third century

BC, Plato’s solution to the problem of ensuring just government was

to train a specialist corps of philosopher kings with no other purpose

but to rule. This classical ideal is reflected in the development in the

late nineteenth century of the British higher civil service as an impartial

elite of well-educated generalists. Today, however, there are pressures

for civil servants to specialise and to be closer to politics and to the

commercial world. Another way of supporting government by an elite

106 General Principles of Constitutional and Administrative Law

is through a text claimed to be divine revelation authoritatively inter-

preted by a priesthood. This solution was rejected in Britain as result

of the sixteenth-century reformation, producing a state church which

over time ceased to have a significant role in government and which

came to support religious freedom.

The opposite perception of government, endorsed by Hobbes, is

that, disagreement is the condition of politics. Rulers are not neces-

sarily wiser or better than anyone else. Indeed it can be argued that

those who seek power over others are the very people least trustworthy

to exercise it. Although Hobbes himself did not address the issue of

controlling power, this perception leads to elaborate separation of

powers structures designed to ensure that decisions are supported with

as broad a consensus as possible between competing groups. The US

constitution provides an extreme example.

5.7.1 The mixed constitution

There are several ways in which the powers of government can be

divided. For example the idea of the ‘mixed constitution’ involves, not

necessarily a distinction between the functions of the different bodies

but ensures that the main interest groups have equal status with no

single body able to act alone so as to check each other and to encour-

age co-operation and compromise. An early version of the mixed

constitution featured in the Roman republic where power was divided

between an aristocratic Senate and elected Tribunes. There is also the

notion of the ‘harmonious constitution’. This goes beyond the mixed

constitution in emphasising what is in effect a safety mechanism, which

requires intervention by one or other of the power-sharing groups in

order to restore the balance where harmony is breaking down. For

example when power is concentrated in an overactive executive with a

frail parliamentary opposition and weak local government it may be

important for the courts to be more active in exercising their powers

(Verde, 2000; see R. v. Secretary of State ex parte Fire Brigades Union

(1995), per Lord Mustill).

The mixed constitution relates to Aristotle’s famous division of con-

stitutions. Aristotle regarded participation in the life of the community

as essential to human well-being. ‘Justice’ consisted of each person

playing his allotted part in the community whether as slave or king, an

idea that throughout history has been used to protect established

interests. He postulated three basic forms of constitution, these being

monarchy which provides authority, aristocracy (literally government

by the ‘best’ people) which provides wisdom, and democracy which

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Constitutionalism: The Rule of Law and the Separation of Powers

provides power. Aristotle thought that each was capable of corrup-

tion: monarchy into tyranny, aristocracy into oligarchy (the rule of a

selfish minority) and factionalism, and democracy into chaos.

During the eighteenth century in particular the British constitu-

tion was often portrayed as a mixed constitution with the King, the

House of Lords and the House of Commons each representing different

‘estates’ or interests. Blackstone (1723–80) praised this arrangement

although he possibly underestimated the dominant influence held by

the aristocracy of his day.

Herein indeed consists the true excellence of the English government

that all the parts of it form a mutual check upon each other. In the

legislature the people are a check on the nobility and the nobility a

check upon the people . . . while the king is a check upon both which

preserves the executive power from encroachments. And this very

executive power is again checked and kept within due bounds by the

two Houses . . . For the two Houses naturally drawing in two direc-

tions of opposite interest, and the prerogative in another still different

from them both, they mutually keep each other from exceeding their

proper limits . . . like three distinct powers in mechanics, they jointly

compel the machine of government in a direction different from what

either acting by itself would have done . . . a direction which con-

stitutes the true line of the liberty and happiness of the country.

Today, the mixed constitution remains in structure but has little

practical reality. The monarch does not by convention exercise a veto

and the House of Lords has lost most of its power over the Commons.

Political parties have replaced the aristocracy leaving the courts as,

arguably, the only effective independent element in the constitution.

On the other hand the doctrine retains some resonance, most recently

in the form of the Report of the Wakeham Commission on Reform

of the House of Lords (2000). A central theme of the report was the

desire, to ensure that the second chamber comprised a mixture of per-

sons, mainly appointed but with a minority elected, who would make

an engineered balance of interest groups deemed worthy by the ruling

elite to participate. Wakeham rejected the idea of a wholly elected

second chamber, on the ground that this might unacceptably restrict

the elected House of Commons and therefore the government.

5.7.2 Montesquieu’s version of the separation of powers

The mixed constitution must be distinguished from what is usually

called the doctrine of the separation of powers. This divides government

108 General Principles of Constitutional and Administrative Law

according to its functions. The doctrine has surfaced in various forms

over the centuries. Locke, for example, distinguished between legislat-

ive, executive and what he called federative functions, these being

concerned with the conduct of foreign affairs. He treated the judicial

function as a particular aspect of the executive. The most influential

version was formulated by Montesquieu in The Spirit of the Laws

(1748). Modifying Locke, Montesquieu distinguished between legisla-

tive, executive and judicial functions arguing that if any two of these

fall into the same hands there is a risk of tyranny. Montesquieu

believed that the British constitution of his time embodied the separa-

tion of powers but possibly did not take into account the extent to

which conventions were beginning to blur the distinction between the

legislature and the executive.

There are three aspects to Montesquieu’s version of the separation

of powers. Firstly separation of function, secondly separation of per-

sonnel and thirdly checks and balances. When the courts refer to the

separation of powers they may therefore use the concept in different

senses. For example in W.H. Smith Do It All Ltd v. Peterborough

[1991] 4 All ER 193 at 196, Mustill LJ remarked, apparently from a

functional point of view that ‘according to the doctrine of the separa-

tion of powers as understood in the United Kingdom, the legislative

acts of the Queen in Parliament are impregnable’. On the other hand,