SIs and SSIs often include references to other laws and regulations (such as Acts, other SIs or EU legislation). These references are accompanied by a footnote which provides the citation of the reference and its legislative history, showing how the referenced provision has been amended by other legislation over time.
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The structure of the footnote will be the following: citation+amended provision+amending history information
For instance: 2016 asp 22. Section 1 was amended by paragraph 11(2) of the Schedule to the Domestic Abuse (Scotland) Act 2018.
2016 asp 22 is the citation of the reference,
Section 1 is the provision referred to which has been amended at some point,
paragraph 11(2) of the Schedule to the Domestic Abuse (Scotland) Act 2018 is the amendment history information relating to that provision.
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These issues with legislaton.gov.uk are often temporary, so you should try to generate the citation footnote again after a short time. If the problem persists then contact Lawmaker support.