Quarantine Flag in Canada

The Canadian rules for the quarantine are prescribed in Memorandum D3-5-1, issued on 11 February 1998 in Ottawa by the Canada Border Service Agency:

15. Where a vessel arrives in Canada flying a yellow quarantine flag (infectious disease), the customs inspector will not conduct normal clearance procedures until advised by the appropriate health authority that it is safe to do so. Pending such notification, the customs inspector, with the help of the local police authority or the RCMP, as deemed appropriate, will endeavour to ensure that the vessel is maintained in a sterile condition pending cancellation of the health alert by the competent health authority.

Quarantine Regulations [C.R.C., c. 1368, Section 15]

Quarantine Regulations Evidence of Immunization Maritime Traffic

15. (1) Every person in charge of a vessel who has received instructions under paragraph 13(b) shall, on approaching a port, display at the fore, as a quarantine signal, a yellow flag by day and a red light over a white light by night, in such a manner that the signal may be readily seen. (2) No person shall remove a signal displayed pursuant to subsection (1) until the vessel has been granted clearance by a quarantine officer."

Source: www.canlii.org

The use of the quarantine flag in Canada is ancient. Quoting Ian Cameron, "Sergey Tolstoy and The Doukhobors: The Halifax Quarantine", Canadian Medical Association Journal 174: 11 (2006): "Jan. 27, 1899 - The ship arrives in Halifax Harbour and hoists the yellow quarantine flag from its mainmast, a signal that a quarantine inspection is required."
Ivan Sache, 18 January 2008