They have statutory authority to do this. DHS Bypasses Environmental Regs to Start Wall Construction.
Well, good. Do it.
If you’re for open borders, or even if you aren’t but have no problem with illegal immigration, I think you might want to take a read of this book: Dreamland: The True Tale of America’s Opiate Epidemic by Sam Quinones.
Lack of a secure border is the great enabler of many social and cultural ills; crime, drug dependence, terrorists, criminals, drunk driving, lower wages for unskilled workers, more people on welfare, emergency room crowding, just to name a few.
A secure border does not have to mean no one from Mexico can here to take landscaping, house cleaning and other low-skilled jobs, it just means they have to do it legally and in way that keep the vicious criminals out.
A secure border actually holds out hope for poor Mexicans by putting pressure on the Mexican government to clean up its dysfunctional and corrupt regime that is making illegal entry in the United States the only hope its poorest citizens have of a better life.
Right now the insecure border with the United States is giving the Mexican government a pressure release valve it does not deserve. It allows Mexico to keep ignoring all the social ills, drug wars and high crime rates that are devastating the lives of so many of its citizens.