The age restriction (which was 28 years old) has been lifted. Here is more info on it:
"The proof of Canadian citizenship for a Canadian born abroad is a Canadian citizenship certificate. A child born outside Canada to a Canadian parent and meeting certain requirements * is a Canadian citizen. However the child will not possess a birth certificate issued by a Canadian governmental authority and for proof of Canadian citizenship, the child will need to obtain a Canadian citizenship certificate. An application must be submitted to obtain this certificate. Although applications are processed in Canada, you may submit the application to a Canadian diplomatic office abroad."
*On April 17, 2009, the rules changed for people born outside Canada. Children born to Canadian parents while the parent are outside Canada will only be Canadian at birth if:
one parent was born in Canada, or
one parent became a Canadian citizen by immigrating to Canada and was later granted citizenship (also called naturalization).
There is an exception to this rule. It does not apply to children born outside Canada in the second or subsequent generation if, at the time of their birth, their Canadian parent is working outside Canada as an employee of the Canadian government or a Canadian province or territory, or serving outside Canada with the Canadian Forces.
How to Apply for a Canadian Citizenship Certificate for a Child Born Outside Canada:
If you were born outside Canada to a Canadian parent on or after January 1, 1947, then send the following supporting documents:
- A birth certificate which lists your parents (issued by responsible government authorities in the country where you were born)
- Proof that one or both of your natural parents were Canadian citizens when you were born i.e. your parent's provincial or territorial birth certificate, naturalization certificate or Canadian citizenship certificate
- Two (2) pieces of personal identification, such as a driver's licence and a health insurance card, one of which must have your photo on it.
- Other documents, such as a marriage certificate/divorce certificate and/or a legal name change certificate (if applicable)
Here are step by step instructions and the application form (CIT 0001): http://www.cic.gc.ca/english/information/applications/guides/CIT0001ETOC.asp#CIT0001E5