SIs are a form of legislation, often drafted by the legal office of the Government Department concerned, allowing the provisions of an Act of Parliament to be brought into force or altered without Parliament passing a new Act.
Because solicitors deal with their clients direct and enter into a contract with them this means that the solicitor can sue for his fees if he is not paid and also allows the client to sue if the solicitor does not do his work.
Laws are made in Parliament and draft laws are called Bills. Bills pass through many stages of consultation and discussion before becoming a law, this is an important part of the democratic law-making process.
The purposive approach can be compared to the mischief rule, but it not only looks at what gap might have existed in the law previously, it tries to identify what Parliament meant to achieve. It looks at the purpose of the Act.