Regardless of whether workers strike over "mandatory" or "permissive" bargaining issues, the NLRA protects their right to strike and they cannot be discharged or disciplined for their strike activity.

NLRA

A key piece of legislation in US labor law, the National Labor Relations Act establishes the rights of workers to unionize and negotiate collectively with their employers.

Mandatory

Refers to something required or obligatory by law or rule.

Permissive

Characterized by or allowing a lot of freedom and flexibility; not strict in the imposition of rules.