Discuss the advantages and disadvantages of extrinsic aids

In R v National Asylum Support Service Lord Steyn stated explanatory notes can ..cast light on the objective setting or contextual scene of the statute, and the mischief at which it is aimed.... So he recognised their value in interpretation.

The use of Hansard has been debated. In Davis v Johnson Lord Denning felt not to use Hansard.. would be to grope around in the dark for the meaning of an Act without switching the light on.... However, it was held he was wrong to have consulted Hansard as it was unreliable and ...promotes confusion not clarity.... Since this case Hansard has been used in limited circumstances and is useful in applying the mischief or purposive approach.

Dictionaries can be used as part of following the literal approach and can increase certainty as it makes the law more understandable and predictable.

Using previous Acts can help determine the mischief an Act has been passed to remedy. International Treaties can be a useful part of the purposive approach, especially when considering laws brought in to give effect to a treaty. For example the European Convention on Human Rights may be useful in interpreting the Human Rights Act 1998.

Extrinsic aids cover a range of resources. It can be argued their use detracts from the original words and meaning contained within the Act. This can be seen in opposition to the doctrine of Parliamentary sovereignty.