Secondary (or delegated) legislation is law made without passing a new act of Parliament. Instead the government uses powers created by an earlier act. The most common form of secondary legislation is statutory instruments. These enable a government to modify or repeal existing legislation without introducing a new bill. Clearly it would be pointlessly time-consuming to enact new legislation every time the government needs to amend or update the detail of existing regulations. However, critics have raised concerns about the growing use of statutory instruments to make more controversial changes. For example, in 2016 statutory instruments were used to abolish maintenance grants for university students and to allow fracking in national parks. Opposition politicians and press commentators argued that the government was sneaking these changes through the back door. Statutory instruments are sometimes called 'Henry VIII clauses' because they enable the government to evade parliamentary scrutiny. Although Parliament can debate and, in theory, reject a statutory instrument, about two-thirds of them simply become law on a specified date in the future, without being put before MPs.