[lowpro]

Free speech applies to to public (government) entities. You can prevent someone from exercising their rights if they are within your private property. In public spaces this isn't the case, as it's public, but an employer doesn't have to allow any freedoms to their employees (minus human rights violations, which are explicitly stated in law).

So a company could say you aren't allowed to say a single word during work hours while working for them. They would also not have employees.