The United States Supreme Court has held that an employer who refuses admittance to his property to nonemployee union organizers has not committed an unfair labor practice if alternative means of communicating to the employees are available to the union.
Lechmere, Inc. v NLRB, US , 112 S Ct 841 (1992).
Labor Law - Unfair Labor Practices - Union Trespassing - Employer Private Property Rights,
Duq. L. Rev.
Available at: https://dsc.duq.edu/dlr/vol31/iss1/9