The place of the doctrine of parliamentary
The Parliament is one of the pillars of separation of powers  and it is the main legislative body in the UK. The theory of parliamentary sovereignty  , which was introduced by Albert Dicey, means that the Parliament can pass the law whichever it is: “Parliament means, in the mouth of a lawyer (though the word has often a different sense in ordinary conversation) The King, the House of Lords, and the House of Commons; these three bodies acting together may be aptly described as the "King in Parliament", and constitute Parliament. The principle of Parliamentary sovereignty mean neither more nor less than this, namely that Parliament thus defined has, under the English constitution, the right to make or unmake any law whatever: and, further, that no person or body is recognized by the law of England as having a right to override or set aside the legislation of Parliament."  Additionally, it implies that the legislative body might amend or revoke any previous legislative acts. Over recent decades the situation concerning parliamentary sovereignty started to change. First of all, in my essay I will introduce the doctrine of parliamentary sovereignty with its advantages and disadvantages, then I will discuss the limits to it and lastly write about the process of future changes.
The concept of parliamentary supremacy firstly appeared in 15th century, when it was set that certain laws could not be changed even by King or Queen.  However, Pocock (1987) argues that it arose from the Acts of Union 1707.  Despite the fact that the notion of Parliamentary sovereignty goes back to middle ages it still mainly refers to Dicey who defined its positive and negative criteria: the positive is that whatever the law is, only the Parliament has the right to make it  and there is no opposing authority while the negative is that there is no authority which can restrict Parliament’s legislative authority: “The principle then of Parliamentary Sovereignty may, looked at it from positive side can thus be described: Any Act of Parliament which makes a new law, or repeals or modifies existing law, will be obeyed by the courts. The same principle, looked at it from its negative side, may be thus stated: “There is no person or body of persons who can, under English Constitution, make rules which override or derogate from an Act of Parliament, or which (to express the same thing in other words) will be enforced by the courts in contravention of an Act of Parliament."  . Modern doctrine of Parliamentary Supremacy can be easily summarized in three main points: first of all, Parliament can pass whichever legislation secondly, ‘no Parliament can bind a future Parliament’ (the only law can be passed which can be amended or reversed by a future Parliament) and thirdly, as Parliament is the highest source of law, a valid Act can never be questioned by courts.  This doctrine of Parliamentary sovereignty differentiates the UK from those countries where constitution inflicts restrictions.
Although the notion of Parliamentary Supremacy with Parliament as the highest lawmaking body has been at the centre of English Constitutional system in recent decades the situation started to change: its sovereignty is now challenged by the limits: internal – reflect political developments in the UK and external – outside the UK. The internal limits include first of all, the devolution of powers to the Scottish Parliament  , secondly, devolution to the Welsh Assembly and thirdly, to Northern Ireland in 1998. It means that since 1998  some prerogatives were delegated to the Scottish Parliament which can make legislation influencing only various domestic issues  i.e. affecting only Scotland and areas not covered by Westminster. However, MPs representing Scotland can vote in the UK Parliament on the issues that do not affect Scotland  .Under certain conditions Westminster still can impose legislation on Scotland  , though these situations had never occurred. Second internal limit is delegation of powers to the Welsh Assembly.  Since 1999 Welsh Ministers are allowed to make laws affecting Wales and make decisions concerning Welsh matters  .Unlike the Scottish Parliament, the Welsh Assembly has power to enact only secondary legislation (‘Assembly Orders’)  The third limit is the Northern Ireland Assembly whose power is something between the Scottish Parliament and the Welsh Assembly: it has legislative power but it is restricted.  Even when the Assembly has power to legislate it should act compatibly with either Human Rights Act or European Law. All these devolutions have certain similarities and they constitute the internal limits to the UK Parliament.
The external limits ‘were seen as of especial significance in the context of a democratic polity’  and they restrict the Parliamentary sovereignty outside the UK. The first external effect put on Parliament is British membership in the European Community  since 1972  which gives rise to complicated matter of two competing supremacies – The UK Parliament and the European Community law.