The British Nationality and Status of Aliens Act 1914, an act of the Westminster parliament, codified the common law rules. Australia followed this with the enacting of the "Nationality Act 1920", which came into effect on 1 January 1921 and codified the concept of a British subject in Australia. In general, the principles of the 1920 Act and subsequent amendments followed United Kingdom legislation, although there were some differences that could lead to a person being a "British subject" solely under Australian law.