he Registration of Canadians Abroad service enables government officials to contact you to provide important information in preparation for an emergency (such as a natural disaster or civil unrest), instructions during emergencies, important changes or updates to the Travel Advice and Advisories for the country for which you registered, and more.
https://travel.gc.ca/assistance/emergency-info/roca-faq
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各国政府针对本国在海外的公民提供自愿登记服务，行之已久，不知道为什么有人这么跳脚？
重要通知！在美中国公民进行“海外公民登记”