The Firearms Act 1920 was partly spurred by fears of a possible surge in crime from the large number of firearms available following World War I and also fears of working-class unrest in this period. "An Act to amend the law relating to firearms and other weapons and ammunition", its main stated aim was to enable the government to control the overseas arms trade and so fulfill its commitment to the 1919 Paris Arms Convention. The ongoing Anglo-Irish War may also have been a factor, as Britain and Ireland were at that time still in union with each other, and the Act also applied to Ireland. It required anyone wanting to purchase or possess a firearm or ammunition to obtain a firearm certificate. The certificate, which lasted for three years, specified not only the firearm but also the amount of ammunition the holder could buy or possess. Local chief constables decided who could obtain a certificate and had the power to exclude anyone of "intemperate habits" or "unsound mind", or anyone considered "for any reason unfitted to be trusted with firearms". Applicants for certificates also had to convince the police that they had a good reason for needing a certificate. The law did not affect smooth-bore guns, which were available for purchase without any form of paperwork. The penalty for violating the Act was a fine of up to £50 or "imprisonment with or without hard labour for a term not exceeding three months", or both.