In the context of labor disputes covered under the National Labor Relations Act (NLRA), the employer with which a union has a labor dispute concerning its employees, such as either an employer:

Under the NLRA, unions have the right, with limitations and qualifications, to engage in picketing about labor disputes that they have with primary employers, as distinguished from neutral employers (29 U.S.C. § 158(b)(4)).

Property owners and worksite managers can confine union strikes or pickets against primary employers at a workplace location, facility or site shared with multiple employers, often called a common situs to particular locations by setting up a reserved gate system. For more information, see Standard Document, Reserved Gate Guidelines.

For more information about union picketing and strikes, see Practice Notes, Employee Rights and Unfair Labor Practices Under the National Labor Relations Act and Labor Law: Overview.