ROBERT SAMUELSON: Yes, Build The Wall.

First, I think it would reduce — though not eliminate — illegal immigration. It would be harder to cross the border; some wouldn’t try. Controlling our border is vital, even if, as the Pew Research Center estimates, there is now some net migration back to Mexico. This could change, and the gross flows in both directions remain large.

Second, the wall would symbolize a major shift in U.S. immigration policy — a tougher attitude — that would deter some from crossing the border illegally and, more important, justify legislation requiring employers to verify workers’ immigration status before being hired. If we were to increase border security but not require proof of legal status, much of the wall’s benefit would be lost. Workers would still come.

Finally, the wall is required as a political act of good faith to immigration opponents. They believe the wall would be effective, and the only way to prove — or disprove — these claims would be to try it. I know and respect many critics of the wall who believe it would be a waste of time and money. They could be right, and I could be wrong, but the only way to find out is to build it.

In the WaPo.