Last night during a rally in Kentucky, President Donald Trump said, “We’re starting on NAFTA very soon”—a signal that renegotiations of the North American Free Trade Agreement may be imminent.

NAFTA created a special nonimmigrant classification permit called the NAFTA TN visa that qualifies Canadian and Mexican citizens to seek temporary entry into the United States to engage in business activities at a professional level. Specifically, the TN visa allows citizens of Canada and Mexico to work in the U.S. in prearranged business activities for U.S. or foreign employers. Visas can be issued only to individuals practicing one of a set of identified professions such as “computer systems analyst."

Under NAFTA, Canadian citizens (unlike Mexican citizens) are not required to apply for a TN visa at a U.S. consulate. If a Canadian has pre-arranged a full-time or part-time job with a U.S. employer and his or her profession qualifies under NAFTA regulations, he or she can be admitted to the U.S. by presenting appropriate documentation at designated U.S. ports-of-entry. Admitted entrants under the TN program are granted an initial period of stay of up to three years but the period of stay can be extended.

An estimated 30,000 to 40,000 Canadians work in the U.S. under the NAFTA TN program. The threat of the U.S. withdrawing from NAFTA puts the TN program at risk, as well as the job status of Canadians currently working in the U.S. under the program; however, even while the NAFTA remains in place, there is growing concern that U.S. immigration officials are adopting an increasingly narrow interpretation of the eligibility of Canadian applicants for permits.

While there has been no public acknowledgment that the eligibility criteria for the TN visa has been tightened, the Trump administration’s anti-immigrant rhetoric, including expressions of concern about highly educated immigrants suppressing the wages of equally highly educated American citizens, might be encouraging U.S. immigration officials to take a harder line on admitting Canadians under the TN program and on extending their stays.

Some support for this possibility is provided by recent reports that specialized Canadian nurses have been stopped from entering the U.S. to work at metro Detroit hospital systems, as well as at hospitals in other U.S. cities. A lawyer working for the Henry Ford Health System in Detroit said he was told by U.S. officials that the advanced nursing skills were "too advanced" for them to fit under the registered nurses category, even though the nurses involved are registered nurses, albeit with more advanced training.

A spokesperson for the U.S. Customs and Border Protection Agency (CBP) denied that any policy alterations have been implemented to change the qualifications for TN status; however, a long-standing concern is that CBP agents have a significant amount of discretion when it comes to assessing the eligibility of foreigners entering the U.S. under the TN program. It would also be somewhat fatuous to believe that the discretion exercised by individual agents, or groups of agents, is not influenced by informal directives from those holding higher positions in the CBP administration.

At one level, it might be concluded that the Canadian economy would actually be better-off if U.S. authorities tightened or even closed their border to highly educated Canadians seeking to work in the U.S. The idea is that any such action would result in an increase in the domestic supply of skilled workers in Canada. This logic is, however, too simplistic, since it ignores other factors. First, Canadians working in the U.S. are presumably better off financially, or otherwise, and their increased welfare counts as a welfare gain for Canada as a whole.

Secondly, many Canadians receive job training experience and skills working for U.S. companies which enables them to be more productive or entrepreneurial when they return to Canada, thereby indirectly benefiting others in the domestic Canadian economy, presuming (reasonably) that returning Canadians do not capture all of the benefits of their improved productivity.

Furthermore, the market connections between U.S. and Canadian economies forged, in part, by cross-border temporary employment of Canadians in the U.S. promotes increased cross-border trade and investment in the longer-run.

In short, the TN program is a beneficial feature of NAFTA for Canada, and Canadian government officials should be alert to the possibility of that program being undermined by informal U.S. government actions, even as the Trump administration remains officially vague about its plans to renegotiate NAFTA.