A National Labor Relations Board memo warns that employment noncompete clauses for nonmanagerial employees are illegal, and some lawyers say it’s the latest sign that employers should think twice about their reliance on such measures.

Noncompete clauses in employment contracts might violate the right of workers under Section 7 of the National Labor Relations Act to take actions that improve their working conditions, NLRB General Counsel Jennifer Abruzzo told the agency’s regional directors in a May 30 memo.