Modern free trade pacts are about more than trade. That’s been known for a long time.

When Canadians were debating free trade with the U.S. in the late 1980s, those challenging the proposed pact warned that it would neuter governments’ ability to act in the public interest.

That charge was repeated in the ’90s during debate over the North American Free Trade Agreement, which linked Canada, the U.S. and Mexico.

The just-completed Canada-European Union free trade pact has sparked similar concerns. So has a recently ratified investment protection agreement with China.

And critics worry that the Trans-Pacific Partnership Agreement talks — which involve the U.S., Japan and smaller Asian nations like Vietnam — will do the same.

In this context, a new study looking at the neutering effects of NAFTA is most useful.

The 41-page analysis, written by veteran trade critic Scott Sinclair and released Wednesday by the Canadian Centre for Policy Alternatives, looks at how the so-called investor-state dispute settlement mechanism within NAFTA has been used over the past 22 years.

This dispute mechanism allows foreign companies to bypass the judicial systems of the NAFTA signatories and directly challenge, before a binding panel, any laws and regulations they think might hurt their businesses.

Here’s what the study shows:

First, at the most basic level, the free-trade skeptics were right.

At the time of NAFTA’s signing, its investor-rights clauses were sold as a necessary way to protect Canadian and American businesses from Mexico’s quirky judicial system.

In fact, as Sinclair’s research shows, relatively few complaints were made against court decisions in Mexico or anywhere else

Instead, 69 of the 77 complaints made against governments in the three countries were levelled against public policy measures in areas such as environmental protection, land-use planning, drug regulation and health care.

Second, the real target was not Mexico but Canada. Over 22 years, 35 complaints were made against Canadian federal and provincial governments by foreign (usually American) companies. By comparison 22 complaints were made against Mexico and 20 against the U.S.

Third, when taking on Canada, foreign companies had considerable but not overwhelming success. Of the 13 cases ruled on to date, Canadian governments have won seven and lost six.

In some cases, the foreign companies were able to win public compensation simply by threatening a NAFTA challenge. In effect that’s what happened in 2013, when the Ontario government paid a U.S.-based company $15 million to withdraw its complaint.

The company had challenged the government’s refusal to let it turn an environmentally sensitive strip of land near Hamilton into a gravel pit.

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Fourth, corporate challenges against Canadian governments peaked in the 2005-09 period but have dropped since.

Why the shift? My guess is that increasingly conservative Canadian governments are giving international investors less reason to be unhappy.

Fifth, and perhaps most important, the U.S never loses.

Of the 11 completed cases brought against U.S. governments, none was decided in favour of the corporate (often Canadian) complainant.

Given that NAFTA’s investor dispute rules are based largely on current American practice, it should come as no surprise that the U.S. does better than Mexico and Canada out of the deal.

Incidentally, this is not just ancient history. Investor-state dispute settlement mechanisms are the flavour of the moment. The just-inked Canada-European Union deal contains, in some areas, stronger protection for foreign investors than even NAFTA.

Does this bother many Canadians? Stephen Harper’s Conservatives and Justin Trudeau’s Liberals think not. They are firmly in favour of all aspects of the Canada-EU deal and think voters won’t punish them for that.

Tom Mulcair’s New Democrats aren’t sure. They haven’t yet decided where they stand.

Correction – January 15, 2015: This article was edited from a previous version that mistakenly said the Canadian government has won six of 13 cases ruled to date.