There exist various pieces of legislation which govern social enterprises and charities, and which legislation this is depends upon which legal form the venture in question has adopted. Where a social enterprise or charity is a company, it will always be subject to the Companies Act 2006, subordinate legislation made under that Act, and related legislation (e.g. the Insolvency Act 1986). However, there may well be other legislation in addition to this which is equally pertinent (in the case of a charity, for example, this will be the Charities Act 2006).
The principal legislation governing CICs, then, is the Companies Act 2006 and related legislation (because a CIC, despite its 'special status', is still a type of company). However, CICs are also subject to their own specific pieces of legislation, the main two being the Companies (Audit, Investigations and Community Enterprise) Act 2004 - which created CICs - and the Community Interest Company Regulations 2005, which regulates them. The Community Interest Company (Amendment) Regulations 2009 contain provisions to enable Scottish charities to convert to CICs and for CICs in general to convert to 'permitted' industrial and provident societies.
Similarly, industrial and provident societies themselves are governed by their own legislative framework. They were brought into being by the Industrial and Provident Societies Act 1965 (which, by virtue of the Co-operative and Community Benefit Societies and Credit Unions Act 2010, has very recently been renamed to the Co-operative and Community Benefit Societies and Credit Unions Act 1965). They are also subject to subsequent legislation such as the the Friendly and Industrial and Provident Societies Act 1968 (Audit Exemption) (Amendment) Order 2006.