The decision is certainly not taken lightly. In a case of criminality, if a person made a written declaration that they had no criminality to declare when in fact they had been charged or convicted prior to taking the oath of citizenship and that comes to our attention, that should be grounds for revocation. In the case of identity fraud, if a person impersonates a deceased family member and that is found out beyond a shadow of a doubt as part of the review of the application, that's grounds for revocation. In the case of residency fraud, if someone declares that they've met the residency requirements for citizenship when in fact conclusive evidence shows that they have not lived in Canada during the relevant period, that should lead to revocation. If I'm not mistaken, all of these decisions can be appealed to courts of law, but these are objective criteria that must be met. When they're not met, revocation follows.
On April 28th, 2014. See this statement in context.