Theoretically yes, according to TIMATIC but convincing the GAS is another matter.
Code:
/ 14AUG08 / 0403 UTC
National CANADA (CA) /Embarkation U.S.A. (US)
Destination CANADA (CA) /Visited U.S.A. (US)
CANADA (CA)
If departing from the U.S.A.:
Passport or NEXUS Card required.
If departing from any other country:
Passport required.
However, passengers claiming to be Canadian Citizens who
present documents other than a valid Canadian passport (such
as a Canadian Birth Certificate or Certificate of Canadian
Citizenship) will also be granted entry ONLY if, following
an examination by a Canadian Border Services Officer, they
satisfy the officer that they are a Canadian Citizen.
If passport replacing documents do not incorporate photograph,
they should be accompanied by supporting government-issued
photo ID (i.e. driver's licence).
In all cases:
Visa not required.
Minors:
1. Parent(s) travelling with a child under 18 years:
are strongly advised to hold documentation showing that the
child is theirs. Parents who are separated or divorced are
also advised to keep legal and other relevant documents in
order to clarify custody rights.
2. Children travelling:
- alone; or
- with adults that have no legal custody over them:
are strongly advised to hold letter of travel consent
signed by legal guardian or parent with legal custody.
Letter of consent should contain:
- authorisation to travel; and
- destination in Canada, stating length of stay; and
- signor's address and phone details.