There is no law for social business per se.
There is however a range of legal structures that can be adopted by a social business.
There are Community Interest companies (CICs), Companies Limited by Guarantee (CLGs), charities and associations. There are a number of laws specific to charities and how they function.
This support is linked to the CSR (Corporate and Social Responsibility) agenda of large corporations and there is also the establishment of specific trusts and associations that provide funding for very specific and targeted purposes.