There are two types of referendum that have been held by the UK Government, pre-legislative (held before proposed legislation is passed) and post-legislative (held after legislation is passed). To date the previous three UK-wide referendums in 1975, was post legislative as the U.K. had joined the eec in 1973,2011 and 2016 were both pre-legislative. Referendums are not legally binding, so legally the Government can ignore the results; for example, even if the result of a pre-legislative referendum were a majority of "No" for a proposed law, Parliament could pass it anyway, because Parliament is sovereign.