A U.S. Border patrol agent opens a gate on the fence along the Mexico border on Jan. 17. (Tomas Bravo/Reuters)

In his Jan. 29 op-ed, "Mexico can thrive without Trump," former Mexican president Ernesto Zedillo hit the nail on the head when he said that many U.S. firms are able to compete successfully around the globe "precisely because they are free to develop links along their supply chains in places such as Mexico — in this case thanks to NAFTA." Mr. Zedillo did not say that U.S. companies' comparative advantage in Mexico is based on low wages resulting from the suppression of labor rights. This is bad for Mexicans (according to official statistics, more than half the population lives in poverty), and it's also bad for U.S. workers who face pressure to accept lower labor standards. The debate over renegotiating the North American Free Trade Agreement should focus on lifting up all working people on both sides of the border.

Manuel Pérez-Rocha, Washington

The writer is an associate fellow
 at the Institute for Policy Studies.

A s a real estate developer, President Trump knows that his threat to build a wall on the southern border is bogus. As former chief counsel of the Federal Highway Administration, I know it, too.

The project inevitably would affect federal lands, as well as environmentally sensitive lands and waterways. Before starting, compliance with numerous statutes and regulations would be required. They include the Environmental Quality Improvement Act, National Historic Preservation Act, Endangered Species Act, Clean Water Act, and laws and regulations protecting Indian lands. Compliance would have to be described in an environmental impact statement. Opponents could challenge the project in federal court.

My experience has been that final approval of such a complex project would take a minimum of 10 years. It is not going to happen. Mr. Trump knows that, and he doesn’t care. He is getting whatever it is he wants anyway.

Anthony J. McMahon, McLean

President Trump's proposed 20 percent tax on imports from Mexico would affect the U.S. health-care system by increasing costs for providers and patients.

Mexico is our third-largest trading partner. Specifically, the United States purchases more than $12 billion in optical and medical equipment from Mexico each year. An additional tax means that we would either lose or pay a significantly higher price for lifesaving equipment and devices. And the burden of taxing these imports would fall solely on the shoulders of Americans, those buying and using the products.

As a physician, I ask Congress and the president to please take this costly and potentially harmful proposition off the table. A wall should not cost Americans their health and well-being.

Lisa Ashe, National Harbor

The writer is medical director of the
Be Well Medical Group.