The short answer is yes, probably, but you may not be able to terminate them for cause.
There are two types of employment terminations in Canada – termination with cause, and termination without cause. The law says that you can terminate an employee at practically any time for practically any reason without cause, so long as you provide them reasonable notice or pay them in lieu of that reasonable notice. These terms may be outlined in the employment contract, or if not are dictated according to previous case law. That is one of the most significant benefits of a contract; reducing the cost of dismissal. Learn more about that here.
Termination with cause though is more complicated. It’s the ‘capital punishment’ of employment law – the employee’s conduct has been so damaging that you are sending them out the door with potentially nothing. For that reason, courts are reluctant to find that just cause for dismissal existed unless the employment relationship has been irreparably damaged. A small breach of a contract or workplace policy will not warrant just cause for dismissal. Continued infractions or problematic behaviour may warrant some sort of performance management, which can include more serious penalties if things do not improve. If there is a serious, ‘culminating’ incident as it is known that is so significant that immediate termination is the only option then that may be another story, but do not make any sudden movements without speaking to a lawyer first.