Is it legal for a company to require that you cannot form or join a union in order for you to be hired?

A family member works for DHL and they are really screwing their workers over. My family member doesn’t even work the job they were hired to do anymore because they changed up everything but they don’t think any of them can do anything about it.

Can anyone help or give advice that I could relay to them to help them form a Union? #Union #unionize #strike #workersrights #labor #Help #USA

@Chromino “Supervisors and managers cannot spy on you (or make it appear that they are doing so), coercively question you, threaten you or bribe you regarding your union activity or the union activities of your co-workers. You can't be fired, disciplined, demoted, or penalized in any way for engaging in these activities.” https://www.nlrb.gov/about-nlrb/rights-we-protect/whats-law
What's the Law? | National Labor Relations Board