Earlier quoted context omitted.
"If I'm legally required to work, isn't that forced labor?" Not if you signed a contract declaring that you will show up. So a strike is in one way organised contract breaching - but one that is allowed under certain circumstances under the bigger contract, the state laws (which you accept by being in that state).
> Not if you signed a contract declaring that you will show up. Yes, even then. A contract violation is not a violation of law. My question is about it being illegal.
False; contract law is, as the name suggests, law, and there are legally established remedies for violations.