The teachers' union recently lost a battle with the provincial government over whether or not they could strike 'mid-contract' to protest political matters. This lost battle for the teachers may, however, be a good sign for their ongoing battle with the provincial over election oriented issue advertising. The court held that the right to strike can be limited despite the fact that it is an interference with freedom of speech. It held that the strike ban is a reasonable limit given the public disruption caused by wide scale teachers' strikes. (The teachers complained that non-union workers were still free to engage in protest strikes -- the court pointed out that this would likely result in consequences such as termination, loss of pay and so forth, something that would not happen to unionized employees).
The government should be concerned about this decision however as there is another battle going on with the teachers over the teachers' right to pay for issue oriented advertising (aka "let's get the Campbell out of here advertising"). Provincial legislation limits such advertising in the run up to a provincial election (that is, when it really matters) and the unions are challenging this ban. Part of the reason, however, the court held that right to strike could be limited is the fact that there are other avenues of protest open to teachers to advance their causes. It certainly seems to me that this is something that weighs in favour of letting the teachers advertise -- if they can't walk, at least they can speak.