The Justice Department’s decision to refrain from unequivocally condemning all no-poach agreements is drawing concern that it could disproportionately hurt low-wage workers.

Legal battles over no-poach agreements, which involve employers agreeing not to compete for each other’s employees, have been brewing in multiple businesses and institutions, including fast-food chains, railways and medical schools.

Such contracts have been traditionally viewed as inherently, or “per se,” illegal. The DOJ, in recent court filings for these cases, agreed that most no-poach contracts are inherently anti-competitive, but some, particularly among private parties in a supply chain, can have pro-competitive benefits.

The DOJ’s intervention further...