Secondary legislation refers to all legislation enacted in the United Kingdom that is not considered an Act of Parliament. Secondary legislation, also called subordinate legislation, exists in two forms: delegated legislation and prerogative legislation. Delegated law mirrors the administrative rulemaking system in the United States, while laws qualifying as prerogative legislation derive from orders of the Crown.
Laws conceived through delegated legislation require approval from the Act of Parliament to pass. Delegated legislation grants certain authorities rulemaking power on a narrow range of subjects. Authorities, like agencies in the United States, create rules under the assumption they possess critical knowledge and expertise in those areas. Prerogative legislation gives the Crown limited rulemaking powers too. Royal government leaders possess the power of creating new laws, provided Parliament approves. Parliament functions as the lawmaking body in the United Kingdom; like Congress, it passes, amends or rejects laws and regulations. Delegated legislation allows expedited law review, revision and passage. It uses statutory instruments, church measures, hybrid instruments and special procedure orders for establishing laws.
Most delegated legislation passes through statutory instruments, which number approximately 3,000 each year. These instruments, called SI, often exist as orders. Parliament accepts or rejects SIs through an affirmative procedure or a negative procedure. Affirmative procedures require explicit approval from both Houses of Parliament. Negative procedures create laws without an official Parliamentary consensus, but allows repeal of order, by either House, through resolutions.