Separation of powers in Australia
The doctrine of the separation of powers in Australia divides the institutions of government into three branches: legislative, executive and judicial. The legislature makes the laws; the executive put the laws into operation; and the judiciary interprets the laws. The doctrine of the separation of powers is often assumed to be one of the cornerstones of fair government. A strict separation of powers is not always evident in Australia; instead the Australian version of separation of powers combines the basic democratic concepts embedded in the Westminster system, the doctrine of "responsible government" and the United States version of the separation of powers. The issue of separation of powers in Australia has been a contentious one and continues to raise questions about where power lies in the Australian political system.
Although it is assumed that all the branches under the separation of powers do not overlap, there is sometimes a ‘common ground’ between all three levels. In Australia there is little separation between the executive and the legislature, with the executive required to be drawn from, and maintain the confidence of, the legislature. In Victorian Stevedoring & General Contracting Co Pty Ltd & Meakes v Dignan the High Court of Australia held that a strict division between these two levels was not practical and re-affirmed the Constitution to outline this (German, 2012).
The first three chapters of the Australian Constitution are headed respectively "The Parliament", "The Executive Government", and "The Judicature". Each of these chapters begins with a section by which the relevant "power of the Commonwealth" is "vested" in the appropriate persons or bodies. The historical context in which the Constitution was drafted suggests that these arrangements were intended to be connected with federal ideas along American lines.
On the other hand, the Constitution incorporates responsible government, in which the legislature and the executive are effectively united. This incorporation is reflected in sections 44, 62 and 64 of the Constitution.
Legislative and executive powers
Section 64 provides that federal Ministers - members of the executive - must sit in Parliament. The specific requirement for ministers to sit in Parliament established the connection between executive and legislative, effectively preventing an American-style separation of the two. Strictly speaking, any person may be appointed a Minister, but their appointment lapses if they do not gain a seat in either house of the Parliament within three months. This provision was necessary in 1901, as the first government was sworn in on 1 January but the first parliament was not elected until late March (see Australian federal election, 1901). No non-parliamentarian was appointed a Minister since then, until the appointment of Bob Carr as Foreign Minister in 2012. However, the provision is still relevant. It applies when a minister in the House of Representatives loses their seat at a general election; despite no longer being a member of parliament, the Minister will typically retain their portfolio for some days after the election, until the new government is sworn in. It also applied when John Gorton became Prime Minister in 1968; he was sworn in while a member of the Senate, then he resigned in order to contest a by-election for a lower house seat, which he won, but between his resignation from the Senate and being elected to the House of Representatives, he remained Prime Minister without holding any seat in Parliament.
In Victorian Stevedoring & General Contracting Co Pty Ltd & Meakes v Dignan, the High Court of Australia held that it was impossible, consistent with the British tradition, to insist upon a strict separation between legislative and executive powers. It was found that legislative power may be delegated to the executive, and as a result upheld the validity of delegated legislation. By contrast, in its insistence on a strict separation of "judicial power", the High Court has been less willing to compromise. 
The executive is not only physically part of the legislature, but the legislature can also allocate it some of its powers, such as of the making of regulations under an Act passed by Parliament. Similarly, the legislature could restrict or over-rule some powers held by the executive by passing new laws to that effect, though these could be subject to judicial review.
The exceptionally strong party discipline in Australia, especially in the lower house, has had the effect of weakening scrutiny of the executive by the legislature since within the lower house, every member of the numerically larger party will almost always support the executive and its propositions on all issues.
On the other hand, the Senate has had the effect of restraining the power of the executive through its ability to query, amend and block government legislation. The result of the adoption of a proportional system of voting in 1949 has been that the Senate in recent decades has rarely been controlled by governments. Minor parties have gained greater representation and Senate majorities on votes come from a coalition of groups on a particular issue, usually after debate by the Opposition and Independents.
The Constitution does, moreover, provide for one form of physical separation of executive and legislature. Section 44, concerning the disqualifications applying to membership of Parliament, excludes from Parliament government employees (who hold "an office of profit under the crown" (iv)) along with people in certain contractual arrangements with the Commonwealth. This was demonstrated in 1992 after Independent MP, Phil Cleary, had won the Victorian seat of Wills. Cleary, on leave without pay from the Victorian Education Department at the time of his election, was held in Sykes v Cleary to be holding an office of profit under the Crown and disqualified. The Court noted that that Section 44's intention was to separate executive influence from the legislature.
Separation of federal judicial power
As early as New South Wales v Commonwealth (Wheat Case) (1915), the High Court decided that the strict insulation of judicial power was a fundamental principle of the Constitution. This also applies to tribunals and commissions set up by Federal Parliament which, unlike some of their equivalents in the states, can only recommend consequences. The Federal Parliament itself has the rarely used privilege of being able to act as a court in some circumstances, primarily where it may regard a non-member as acting "in contempt" of parliament.
The reasoning in the Wheat Case was taken further in Waterside Workers' Federation of Australia v JW Alexander Ltd (1918). A decisive distinction between judicial and arbitral functions was drawn.
A consequence of the Australian version of the separation of powers is its role in encouraging judicial deference to the "political" arms of government. The normal propensity of the High Court is to recognise that separation of powers requires not only that the "political branches" should not interfere with judicial activity, but also that the judiciary should leave politicians and administrators alone. The importance of deference has been acknowledged in extrajudicial writings, and in decisions such as Drake (No 2).
Separation of powers in the States
While there are strong textual and structural bases for the independence of the judiciary in the Commonwealth Constitution, the same is not true of the State constitutions. State courts, unlike their federal counterparts, are therefore capable of exercising non-judicial functions. For example, the District Court of South Australia, through its Administrative and Disciplinary Division, conducts merits review of administrative decisions, a function which at Commonwealth level can only be exercised by Executive tribunals. Nevertheless, a degree of judicial independence is maintained at State level by convention.
The federal separation of powers also has implications for State courts, due to the fact that State courts may be invested with federal judicial power under section 71 of the Commonwealth Constitution. On this basis it was held in Kable v Director of Public Prosecutions (NSW) that a State court could not be given a function inconsistent with its status as a potential repository of federal judicial power. This principle was recently applied by the High Court in South Australia v Totani in relation to the Serious and Organised Crime (Control) Act 2008 (SA). Section 14(1) of the Act required members of the Magistrates' Court of South Australia to make control orders on application by the Commissioner of Police, provided only that the Magistrate was satisfied that the person subject to the control order was a member of a declared organisation. Even though the functions of the Magistrates' Court under the Act are purely a matter of South Australian law, the fact that the Court is also capable of exercising federal jurisdiction was held to require that it maintain certain standards of independence and impartiality so that it retain the character of a court.
Parliamentary scrutiny of the executive and, in particular, by the New South Wales Legislative Council, was tested in the 1990s when Treasurer Michael Egan, on behalf of Cabinet, refused to table documents in the Legislative Council of which he was a member. The Council, determined to exercise its scrutiny of the executive, pressed the issues and eventually adjudged the Treasurer in contempt, suspending him from the house twice. The matters were disputed in three cases in the High Court and the Supreme Court of New South Wales. The results upheld that principle that the Legislative Council does have the power to order the production of documents by a member of the House, including a minister, and can counter obstruction. However, the extent of the Legislative Council's power in relation to Cabinet documents remains unclear.
- Victorian Stevedoring & General Contracting Co Pty Ltd v Dignan; sub nom Meakes v Dignan (1931) 46 CLR 73 
- Kable v Director of Public Prosecutions (NSW) [1996 HCA 24]
- Sykes v Cleary  HCA 60; (1992) 176 CLR 77 (25 November 1992) .
- see also R v Kirby; Ex parte Boilermakers’ Society of Australia (1956) 94 CLR 254 AustLII
- Hilton v Wells  HCA 16; (1985) 157 CLR 57 (14 March 1985) AustLII. See also Grollo v Palmer  HCA 26; (1995) 184 CLR 348 (21 September 1995) AustLII.
- Kable v Director of Public Prosecutions (NSW) (1996) 189 CLR 51 at 25 AustLii.
- South Australia v Totani  HCA 39 AustLII
- Egan v Willis  HCA 71; (1998) 95 CLR 424 (19 November 1998) AustLII. See also Egan v Chadwick  NSWCA 176 (10 June 1999) AustLII.