One of the three branches of government, the others being the legislature and the judiciary. In a sovereign state the executive consists of the person or body with the power to determine the policy of the state. In most modern states the composition and powers of the executive are defined in a written constitution. The major exception to this is the UK, which does not have a written constitution, but the composition and powers of the executive remain constitutionally limited by tradition, convention, common law, and statute.
Dictatorships In some states, such as absolute monarchies in the past or modern dictatorships, both totalitarian and non-totalitarian, executive power may be wielded by a single person or by a small group of people who are not in practice subject to any constitutional restraints. In such cases the existence of a constitution may be intended to and may indeed confer an aura of legitimacy on those who exercise political power.
Liberal democratic states In liberal democratic states the executive is subject to various types of constitutional restraint. In the case of a parliamentary system, such as the UK, this restraint takes the form of making the executive constitutionally responsible to the legislature. In order to assume and continue in office the executive must have the support of a majority in Parliament, and its programme is subject to parliamentary approval. Members of the executive are invariably drawn from the legislature and are expected to explain and defend the executive's policy in the legislature. The judiciary is normally made independent of the executive and the legislature in dispensing justice, but remains constitutionally subordinate to the other two branches.
Presidential-congressional systems In presidential-congressional systems, of which the United States is the most important example, the three main branches of government are separated and their respective powers are defined in the constitution. In the case of the United States the personnel of the three branches are separate. The president and members of Congress are elected at separate elections and for different terms of office. Holders of executive office may not be members of Congress and vice versa. The president is not constitutionally responsible to Congress and the existence of the executive is not dependent on support in Congress. The president cannot dissolve Congress in the hope of securing a legislature more amenable to his or her point of view and Congress cannot get rid of a president whose policies it does not like, unless it is prepared to use the extreme weapon of impeachment.
There are, however, a number of ‘checks and balances’. For example, although Congress is primarily responsible for all legislation, the president must sign all bills in order to give them the force of law. The president can therefore veto bills passed by Congress, although Congress can override this veto by re-passing the legislation by a two-thirds majority. Similarly, the United States Senate must approve all treaties signed with foreign powers and give its assent to the president's nominations for various offices, including members of his cabinet.
Hybrid constitutions France under the constitution of the Fifth Republic is an example of a hybrid constitution involving some features of the parliamentary system and some features of the presidential-congressional system. There is thus a partial separation of powers in that the president of France has certain executive powers, but is not constitutionally responsible to the French parliament, whereas the prime minister and the cabinet, whilst they may not be members of the Senate or National Assembly, are constitutionally responsible to the latter.
Federal systems A further division of executive power may be found in federal systems, in which executive, legislative, and judicial power is constitutionally divided between national and regional systems of government. Such a division should not be confused with the American separation of powers, which as already noted, is the division of power between the three branches of government. A federal division of power may exist in a parliamentary system (for example, Australia and Canada) or in a presidential-congressional system, as it does in the United States.