The Canadian Government has issued the following warning about dual citizenship.
Dual citizenship occurs when a person is the citizen of more than one country. Canadian law permits dual citizenship: you can remain or become a citizen of another country and still be recognized as a Canadian.
But dual citizenship (also called dual nationality) is not legally recognized in all countries and can lead to serious difficulties for Canadians when they are in the country of their second citizenship. It can also create problems in third countries if there is any confusion over what citizenship was used to obtain entry.
There are also risks and problems associated with having more than one citizenship.
RECOGNITION: The most important of these is that your Canadian citizenship may not be recognized in the country of your second citizenship. The authorities of that country may not recognize Canada's right to provide you with consular assistance. There could also be problems in other countries, especially if you used the travel document of the country of your second citizenship to gain entry. In such circumstances, the local authorities could decide that Canada does not have the right to provide consular assistance.
MILITARY: Many countries still have compulsory military service. If you are a citizen, and you meet other conditions, you may be legally required to register for military service and to respond to call-up orders. This legal obligation may exist even if you do not reside in the country of your second citizenship. Your obligations could be enforced even if you're just visiting at some point in the future.
TAX: Taxation arrangements between countries are complex. If you hold dual citizenship, you may have obligations in both countries. These obligations should be discussed with your financial and/or legal advisers.
MARRIAGE: Canada recognizes the legality of marriages performed in other countries. However, marriages performed in Canada may not always be considered legal in other countries. Similarly, divorce and child custody documents issued by Canadian courts may not be recognized.
CHILD ABDUCTION: Many international child abductions involve parents and children who have dual citizenship. If the abducting parent carries a second passport, Canadian authorities may encounter difficulties in preventing the abduction. The Government of Canada cannot prevent another country from providing passport services to Canadian parents or children who are also citizens of that country. You or your lawyer can request that a foreign diplomatic or consular mission not provide passport services for your child. To do so, provide the mission with a written request, along with a certified copy of any court orders dealing with custody or foreign travel by your child. Inform the foreign diplomatic or consular mission that you have also sent a copy of your request to Consular Services of Foreign Affairs and International Trade Canada in Ottawa.
USE YOUR CANADIAN PASSPORT: The Canadian government strongly encourages you to use your Canadian passport when travelling abroad, especially when entering the country of your second citizenship. Note that you cannot use a Certificate of Canadian Citizenship instead of a Canadian passport to travel abroad.
Click here for details from the Department of Foreign Affairs.