It is ... generally true that wilful disobedience of an order will justify summary dismissal, since wilful disobedience of a lawful and reasonable order shows a disregard--a complete disregard--of a condition essential to the contract of service, namely, the condition that the servant must obey the proper orders of the master, and that unless he does so the relationship is, so to speak, struck at fundamentally.
--Laws v. London Chronicle Ltd. 
Much has changed in the last half-century in employment, including the purge of words like "master" and "servant" from our workplace vocabulary. One thing that has not changed is the foundation of employment that employers control the employees' work. It is not up to employees to "consider the wisdom" of employer instructions as long as they are legal, safe and within the compass of one's job. (Stein v. British Columbia Housing Management Commission (1992), CanLII 4032 (BC CA)) Even experts who think they are better qualified than their bosses must submit.
Even a single act of disobedience that is not otherwise of a grave and serious nature, if it is clear and wilful, may be sufficient to justify firing if it can be seen as an employee repudiation of the employment relationship. Nevertheless, the real world is characterized by more tinges of gray than laser blacks and whites. Insubordination--the failure to submit to the authority of the employer--the state of disobedience, rebellion and mutiny--is not always easy to identify to a point where one would feel legally secure in firing the employee. Judges today are inclined to grant employees second and third chances (on the basis that everyone is entitled to a bad day once in a while) and expect employers to progressively discipline recalcitrant employees.
In this article, we set out a few judicial decisions that come down on both sides of the insubordination issue.
Amos v. Alberta--the Employer Wins
Even a single act of disobedience that is not otherwise of a grave and serious nature, if it is clear and wilful, may be sufficient to justify firing if it can be seen as an employee repudiation of the employment relationship.
Steve Amos, a computer systems analyst working for the government of Alberta, "entered the room and, in a belligerent tone and loud timbre, told Varma (his supervisor) that he should not be taking shit from users, but that he should be giving shit to them." (para 12) He had, on "many earlier occasions" told his...