The Special Restriction (Coloured Alien Seamen's) Order is described by Laura Tabili as 'the first instance of state-sanctioned race discrimination inside Britain to come to widespread notice' (p. 56). The work of the Home Office Aliens Department, the Order was issued under Article II of the Aliens Order of 1920 and stated that 'coloured' seamen who did not possess documentary proof of their status as British must register as 'aliens' in Britain 'whether or not they have been in the United Kingdom for more than two months'. Police were to apprehend 'coloured' men disembarking from ships and report them to the police if they failed to show their documentation. In practice, it was not easy for 'coloured' seamen to prove that they were British subjects because sailors were not required to carry passports and, unlike those of their white counterparts, 'coloured' seamen's discharge certificates were not considered proof of their nationality because of allegations of trafficking in these papers.

Reasons for the issue of the Order are various and debated. In a letter dated 14 August 1926, the Under-Secretary of State cites the demands made at the end of the First World War by the National Sailor and Fireman's Union that 'steps should be taken to restrict the admission to this country of coloured seamen who could not establish that they were British subjects, since they competed in the overstocked labour market for seamen and were a source of grave discontent among British sailors', and claims that the accumulation of 'coloured seamen' in certain ports 'was a continual source of irritation and...likely to lead to a breach of the peace' (HO 45/12314). However, by the mid-1920s, employment in the shipping industry was beginning to pick up, which calls these reasons into question. Further, historians have recently questioned the role of the Union in pushing forward this piece of legislation, arguing that it was the state that played a more significant role.

State officials, determined to deport 'coloured' seamen, interpreted and enforced the rules rigidly, depriving these men of their citizenship. The India Office and Colonial Office received numerous protests from seamen who claimed that police were using the order to target men who were obviously British subjects. Further, officials erroneously applied the rules to non-seamen, for example registering 63 Glasgow-based Indians, most of whom worked as peddlers and labourers, as 'aliens'. Indians in Liverpool protested in the form of a public rally and through founding the Indian Seamen's Union, led by N. J. Upadhyaya. The India Office, fearful of the public outcry triggered by the Order in India, reprimanded the Home Office, even suggesting that all Indians should be issued with passports - a suggestion that was not received favourably by the Home Office. Finally, it was agreed that Indian seamen registered as 'aliens' could apply to the Home Office to have their British nationality verified. They would then be issued with a Special Certificate of Identity and Nationality which would enable their registration to be cancelled. The Order was finally revoked in 1942.