Unveiling a long-awaited plan to combat the national scourge of opioid drug addiction, U.S. President Donald Trump called Monday for stiffer penalties for drug traffickers, including the death penalty.

"Toughness is the thing that they most fear," Trump said.

Opponents call that a return to failed drug-war tactics, and some legal experts question its constitutionality and effectiveness.

"This isn't about nice anymore," Trump said. "This is about winning a very, very tough problem and if we don't get very tough on these dealers it's not going to happen folks… I want to win this battle."

The president formalized what he had long mused about publicly and privately: that if a person in the U.S. can get the death penalty or life in prison for shooting one person, a similar punishment should be given to a drug dealer who potentially kills thousands.

Opioids, including prescription opioids, heroin and synthetic drugs such as fentanyl, killed more than 42,000 people in the U.S. in 2016, more than any other year on record, according to the Centers for Disease Control and Prevention.

What is Trump's plan?

The push for greater use of the death penalty is just part of a sweeping plan that includes stiffer penalties for drug peddlers as well as expanding access to treatment and recovery efforts. It's in keeping with the Trump administration's tough-on-crime approach to the opioid abuse epidemic.

Trump, who mused openly that countries like Singapore have fewer issues with addiction because they harshly punish drug dealers, said he wants the Justice Department to seek the "ultimate penalty" when possible.

He also announced a new website, www.crisisnextdoor.gov, where members of the public can share stories about the dangers of opioid addiction.

Cataldo Ambulance medics and other first responders revive a 32-year-old man who was found unresponsive and not breathing after an opioid overdose on a sidewalk in the Boston suburb of Everett, Massachusetts, U.S., August 23, 2017. (Brian Snyder/Reuters)

Can the Justice Department seek the death penalty for drug dealers?

Maybe. Trump isn't proposing a new law, but is encouraging the Justice Department to enforce existing laws more vigorously.

The Federal Drug Kingpin Act allows federal prosecutors to seek the death penalty in cases when someone is intentionally killed during a drug deal or in furtherance of a drug enterprise.

There are other federal laws that could potentially allow death penalty prosecutions of "kingpins" when large amounts of money and drugs are involved, even if there has not been a killing. But no administration, Democratic or Republican, has ever pursued and secured a death sentence under those laws.

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It's not clear that death sentences for drug dealers, even for those whose product causes multiple deaths, would be constitutional, said Doug Berman, a law professor at Ohio State University. He predicted the issue would be litigated extensively and ultimately settled by the U.S. Supreme Court.

"The death penalty is uncertain as a constitutionally permissible punishment without that connection to an intentional killing," Berman said.

Trump's attorney general, Jeff Sessions, vowed to seek the death penalty under federal law "whenever appropriate" against drug dealers who "show no respect of human dignity and put their own greed ahead of the safety and even the lives of others."

Have drug traffickers ever been sentenced to death?

The Death Penalty Information Center lists 14 federal death row prisoners awaiting execution for drug-related crimes. They include Azibo Aquart, who was sentenced to death in 2012 for planning and participating in the deaths of a rival and two people living with her. There is also Orlando Hall, who was sentenced in 2007 for a drug-related kidnapping that ended in death. Dustin Honken was sentenced to die in 2004 for the killings of two children in a drug-related conspiracy in which three other people were also killed.

Will more federal death sentences ease the drug epidemic?

Trump believes so, but others are skeptical.

Cornell Law School Professor John H. Blume said enforcement of the Federal Drug Kingpin Act tends to net poor minorities considered low- to mid-level drug dealers rather than kingpins whose products are fueling the drug crisis. Opponents said the approach resembles the drug war of the 1970s and '80s, when there was bipartisan agreement in Washington that the best way to fight crime was with long, mandatory prison sentences. That approach is now questioned by some conservatives as well as liberals.

"I don't think there's any reason to believe that attempting to revive this policy and use it more effectively will be any more successful," Blume said, adding that death sentences are hard to win. Too few drug traffickers will be sentenced to death and executed to have a real deterrent effect, he said. "I don't think people out there who sell drugs are worried about, am I going to get the death penalty?"