Please see latest interpretation from USA Referees:
Subject: Fw: Lineout – No maul
At a lineout, if a defensive team decide not to compete and not join to form a maul when the offensive team takes the ball and forms what they anticipate will be a maul, communicate to the offensive team to get the ball out. If they do not get the ball out or they move toward the opposition goal line, then call a scrum for accidental obstruction, on the first occasion, and tell that team that if it occurs again, you will be forced to Penalize them.
Always communicate first, and give the team an opportunity to comply. The reason for this is that we are not in the business of teams milking penalties.
National Panel Manager
USA Rugby Referees