President Donald Trump speaks about combating the opioid crisis on...

President Donald Trump speaks about combating the opioid crisis on Monday in Manchester, N.H. Credit: AFP / Getty Images / Mandel Ngan

If you can be scared by death threats, whether from the president of the United States, another drug dealer or an addict looking to rob you of cash and product, you’ll never make it as a drug trafficker.

It was, even before President Donald Trump’s announcement Monday that he will seek the death penalty for big dealers, a very dangerous job.

That’s not to say Trump’s dealer-death penalty idea has much downside. If some guy is selling fentanyl or heroin that kills a bunch of people, it’s hard to argue he shouldn’t get the death penalty. But that penalty won’t help solve the problem.

It’s the same with Trump’s border wall. It’s just something that won’t help much in trying to stop illegal drugs or unauthorized people from coming here.

You would actually think our businessman president would get this. You’d hope he could understand market economics.

The market will always find a way to supply demand. So when society wants to stop or reduce any kind of consumption, it has to find a way to reduce demand. If not, nothing will change.

Walls won’t help that, nor will death threats against people who have already accepted dying as a potential downside of their chosen profession.

Consider illegal immigration to the United States. It is a problem that (if you believe it is a problem) is one of demand. Employers and consumers have created a tremendous market for labor priced so low, in exchange for work so hard, that too few native-born Americans or legal immigrants will take the jobs.

It is not an unsolvable problem, but it is one that we cannot solve by trying to cut off the supply. We’d have to cut off the demand.

And this is a policy area where the death penalty could really help.

If the United States were to impose the death penalty on employers who hire unauthorized workers, pretty quickly there would be hardly any unauthorized workers in the United States. And if they leave or don’t come, their dependents would do the same.

We have a system called E-Verify that can tell employers if workers are eligible to work. About 750,000 of our nation’s employers participate — out of 18 million businesses. And experts say cheating by participants is common and penalties rare. That’s not surprising when you consider that only 3,000 employers participating in the program were audited in the eight years of the Obama administration.

As long as people from other countries who are not authorized to be here can build better lives here, they will come. They will come by boat and land and airplane. Some will sneak in and some will overstay visas. It’s legal for people from other countries to visit Walt Disney World and New York, and it’s easy for them to stay, if they can get by.

Now consider drugs. The United States has a long history of trying to stop the supply of intoxicants its residents crave, with little success. Prohibition didn’t work. Three decades of attempts to stop cocaine trafficking were so unsuccessful the drug now costs users 60 percent less than it did in 1985. Fentanyl can as easily be produced in the United States as China. And drugs can come in over the northern border, by mail or in a boat, not just via Mexico.

If we want to control drug use, we must change the fact that so many Americans feel the need to be so very high. If we want to stop illegal immigration, we’re going to have to prosecute employers who cheat, rather than persecuting foreign workers they exploit.

Threatening poor foreigners, and fearless drug traffickers, won’t accomplish anything.

Lane Filler is a member of Newsday’s editorial board.