The Scandinavian countries are generally quite similar in these matters. In Denmark, uniformed police can't strike. It's part of the way they're employed, in return, they're almost impossible to fire except for cases of gross violation of their duty. I'm almost certain Sweden is the same, but I'd love for a Swede to chime in. It's called Tjenestemænd in Danish.
Can you point to a concrete law stating this?