79. Notwithstanding any act or regulation to the contrary, when a professional syndicate or a union or federation of professional syndicates is entrusted with the carrying out of a plan, no producer bound by the plan who is a member of such a syndicate or of a syndicate forming part of such a union or federation is required to pay the assessment payable to be a member of that syndicate for a year during which contributions must be withheld out of amounts attributed to that producer to be remitted to the syndicate, union or federation under a by-law, homologated agreement or arbitration decision.