Secondary activity occurs if a union pressures a neutral third party in order to gain leverage against an employer with whom the union has a labor dispute. NLRA § 8(b)(4) prohibits various kinds of secondary activity.

I. What’s Secondary Activity?

Let’s consider an example of secondary activity.

Suppose an employer provided janitorial services to commercial clients. The employer and the union representing its employees were involved in a wage dispute. The union picketed outside the nearby...