Yes, you can be restricted in what you say in the workplace. But your employer cannot restrict what you say outside the workplace about the workplace if you are willing to bear the consequences.

Your employer can also review your email, go through your desk, tap your phone, and even put cameras in the bathroom. However, a smart employer will check with his lawyer before doing ANY of these things. An employer who goes through a desk without a witness present risks having the employee say, "So that's where that envelope with the $25,000 I had in my desk drawer went!"

There are different rules for those working in the public sector.