The Canadian, Mexican and US governments signed the NAALC, the first labour agreement negotiated as part of an international free trade agreement, on September 14, 1993 and it came into force along with its parent trade agreement, NAFTA, on January 1, 1994.

In theory, as described on their website, the NAALC is supposed to provide “a mechanism for member countries to ensure the effective enforcement of existing and future domestic labor standards and laws without interfering in the sovereign functioning of the different national labor systems.” The goal is to “improve working conditions and living standards, and to protect, enhance and enforce basic workers’ rights” via specific Objectives, Obligations and Labor Principles that the three signatory governments are bound to uphold.

In the case that one of the governments fails to uphold its own labour laws, any non-governmental organization, individual, union or employer can submit a complaint to the National Administrative Office (NAO) of their own country. These Public Communications, as they are called, are handled through non-judicial hearings. Based on their conclusions, the NAO then has the option to recommend further actions via Ministerial Consultations. If the parties are not satisfied after these negotiations, the NAO can request that the complaint be submitted to an Evaluation Committee of Experts (for matters related to NAALC Principles 4 – 11) and, finally, to an independent Arbitral Panel.

When the NAALC was negotiated, it was seen by many as an attempt by newly elected US president Clinton to justify signing the North American Free Trade Agreement (NAFTA), which he had campaigned against for its lack of enforceable labour standards.

Prime Minister Jean Chretien had also campaigned against NAFTA, promising to renegotiate the agreement if his party were elected.

The MSN/CAT/USAS complaint is one of 28 in the ten-year history of the NAALC and only the second case that has been accepted by the Canadian NAO. The only other complaint investigated by the Canadian NAO was concerning the enforcement of laws on freedom of association and health and safety at the maquila ITAPSA, an auto-parts factory in Ciudad de los Reyes in the State of Mexico.

That complaint was submitted in April 1998 by the Canadian office of the United Steelworkers of America together with 11 other unions and 31 concerned organizations in the three countries, and resulted in Canada requesting ministerial consultations with Mexico.

In January of 2003, the Canadian government announced that Ministerial Consultations had concluded and that Canada was satisfied that problems related to freedom of association had been adequately addressed by reforms to Mexican labour law, which democratic unions in Mexico oppose.

Although the NAALC process includes a number of stages, to date, none of the 28 complaints to the U.S., Canadian or Mexican NAOs has resulted in serious action beyond the Ministerial Consultation stage. According to Linda Delp of the UCLA Center for Labor Research and Education, "unless the governments make a serious effort to resolve the problems in the current [Puebla] case, the side agreement will fade into oblivion as a failed experiment to protect workers' rights in a global economy."

• Read more about NAALC and the Puebla case