The tension over how to define an employee in a burgeoning gig economy was recently on display: A new federal opinion letter tilted things in a pro-employer direction, making it easier to classify someone as an independent contractor, and a court ruling on a California standard tilted them the other. In between, New Jersey reiterated its pro-worker mandates.

The Labor Department released an opinion letter April 29, addressed to an unnamed concern in the gig economy, suggesting that companies can lean on contractors in the work relationships increasingly typical for technology companies—without the complications of providing certain employee benefits...