To go on a strike means that there is a cessation in work, a refusal to work or a refusal to continue to work by two or more employees. A worker would go on strike because there terms and conditions are not being met.
To be locked out incluides the closing of a place of employment by an employer, the suspension of work by an employer or a refusal by an employer to continue to employ employees for the purpose of compelling employees to agree to terms of conditions of employment. A worker would be locked out if the employer basically locks them out of work.
The canadian governments can force them back to work because the canada post is the mail and air canada is planes. The mail i understand can be forced back to work because what if someone needs there cheque so that they can pay for a serious operation or there bills or food. If no mailmen were working how are we supposed to do that. The planes are somewhat harder to understand. But people need to be places and air canada is maybe a part of the canada post so they need air canada to help deliver the mail everywhere.
The Air Canada workers were striking because 3 workers were suspended for heckling Federal Labour Minister Lisa Raitt, when other workers heard of the suspensions they started striking. The Canada Post workers were striking because they think they had to much work for to little pay so they wanted less work an more pay. They said its getting much harder every year because more and more people need more and more mail.