On 2 April 1997, the National Assembly adopted a new Constitution. It replaced the Constitutional Law on the Relationships between the Legislative and Executive Powers and on Local Self-government, known as the Small Constitution, which had been in force since 1992. The new Constitution was approved in a popular referendum on 26 May 1997, signed by the President and published on 16 July 1997. The Constitution finally entered into force on 17 October 1997. The new Constitution had been under discussion since 1989, but several earlier attempts to adopt a new constitution had failed. According to the new constitutional provisions, constitutional amendments may only be proposed by at least one-fifth of the statutory number of Sejm deputies, by the Senate, or by the President of the Republic. A Bill to amend the Constitution needs to be adopted by the Sejm by a majority of at least two-thirds of the votes and in the presence of at least half of the statutory number of deputies, and by the Senate by an absolute majority of votes in the presence of at least half the statutory number of senators. If changes are to be made to chapters I, II or XII of the Constitution, the initiators of such changes may call for a popular confirmatory referendum. Poland has traditionally been part of the continental law tradition. Even under communism, the country did not break with this legal heritage. The legal system of Poland is based on a hierarchy of legal norms.