What is meant by the doctrine of Parliamentary sovereignty (supremacy)?

Parliamentary sovereignty is the idea, originating in this form in the United Kingdom legal system, that ‘Any Act of Parliament, or any part of an Act of Parliament, which makes a new law, repeals or modifies an existing law, will be obeyed by the Courts’ (A.V. Dicey) – this latter element is thus labelled ‘implied repeal’. This idea is not contained in any law and it is thought not to be from a legal source, but from a historical one. Courts have in a way allowed and encouraged Parliamentary supremacy in the common law, and have emphasised the UK Parliament has unlimited legislative supremacy, and judges are merely there to give effect to enactments of Parliament.
There are however limits to parliamentary sovereignty regarding EU law and laws affecting human rights, in the cases of Factortame and Simms respectively. These demonstrate an erosion of the idea of parliamentary sovereignty in the UK. It has been later argued (in Thoburn v Sunderland City Council) that there is a distinction between ‘constitutional’ statues and ‘ordinary’ statutes. The former are very important statutes of a ‘constitutional’ nature, such as the Magna Carta, Human Rights Act 1998, European Communities Act, which should not be automatically overridden by the principle of implied repeal.