Wikipedia
Act of Sederunt (literally Act of Session; with sederunt a term meaning a session or meeting of a court.) in Scots law, is an ordinance for regulating the forms of judicial procedure ( hearings and trials) before the Court of Session (the supreme civil court of Scotland), sheriff courts in civil session, and for setting fees for messengers-at-arms and sheriff officers enacted by the Lords of Session under authority of a power originally conferred on the founding of the Court of Session in 1532 and granted exclusively to them by an act of the Parliament of Scotland in 1540, c. 93. The power to pass Acts of Sederunt was reconfirmed by the Parliament of the United Kingdom in the Court of Session Act 1988. Further powers have been added to regulate the civil procedures of the sheriff courts of Scotland by the Sheriff Courts (Scotland) Act 1971, along with powers to set fees for messengers-at-arms and sheriff officers who are responsible for serving writs, decrees and diligences in Scotland. The College of Justice regulates procedure for criminal trials through Acts of Adjournal. A quorum of nine judges is required to pass an act of Sederunt.
Acts of Sederunt take effect as a form of secondary legislation as a Scottish Statutory Instrument but are only laid before the Scottish Parliament where required by statute. Whereas in England and Wales the Civil Procedure Rules are drawn up by the Civil Justice Council and are laid before Parliament as a Statutory Instrument subject to negative procedure.