Under the policy, illegal immigrants from China could stay in Hong Kong if they reached urban areas and found a home with their relatives or other forms of accommodation.
[4]: 4 Prior to the Sino-Japanese War, movement across the border between China and Hong Kong was largely unregulated, and Chinese immigrants were not required to carry travel documents.
[3]: 2 In an attempt to halt this influx of immigrants, a Frontier Closed Area was established by the Hong Kong Government along the border with China in June 1951, and expanded to its largest limit in 1962.
Illegal immigrants arriving on or after 24 October 1980 were repatriated immediately, and it became compulsory for Hong Kong residents to carry their identity cards in public areas.
Police will randomly check citizens' Hong Kong Identity Card for spotting out Mainland Chinese illegal immigrants, other than searching for other criminal suspects.