WASHINGTON — Howard Wooldridge, a Washington lobbyist, is a former detective and forever Texan on an important mission — trying to persuade the 535 members of Congress to end the federal war on marijuana.

Liberals tend to be an easier sell than conservatives. With liberals, Wooldridge dwells on the grossly racist way the war on drugs has been prosecuted.

“The war on drugs,” he tells them, “has been the most immoral policy since slavery and Jim Crow.”

Conservatives hear a different argument, but one that Wooldridge holds every bit as dear: “Give it back to the states.”

This is a case for states’ rights, a doctrine to which conservatives habitually declare their loyalty. It is based on the 10th Amendment to the U.S. Constitution, which says that powers not delegated to the federal government are given to the states or to the people. In fact, states had jurisdiction over marijuana until 1937.

Co-founder of a group called Law Enforcement Against Prohibition, Wooldridge leaves no doubt where he stands on the war on drugs. End it all. That means no more U.S. Drug Enforcement Administration. No more federal SWAT teams invading suburban backyards. No more DEA agents shooting from helicopters.

Today the war on drugs costs taxpayers $12 billion a year just for the enforcement part. Meanwhile, the loss of income for the millions of ordinary Americans made nearly unemployable after being caught with a joint can’t be counted.

“You could close half the prisons in the country if you ended prohibition,” Wooldridge says.

He now focuses only on marijuana, which he dismisses as “little green plants.” And he doesn’t use the L-word — that is, legalization.

If Washington state and Colorado legalize marijuana for recreational use (and they have), that’s fine with him. If 21 other states, from Maine to Hawaii, choose to allow marijuana only for medicinal use, that’s also OK. And if Alabama and South Dakota want all marijuana kept illegal, again, fine.

“For sure, Utah is smokeless,” he added, “and I say God bless.”

Liberals have traditionally shunned states’-rights arguments because of their association with the evils of slavery and segregation. So it is notable that the NAACP has endorsed a bill just submitted by Rep. Dana Rohrabacher, R-Calif., requiring the federal government to respect state laws on marijuana.

African-Americans do not like the 10th Amendment, Wooldridge notes, “but the racism involved in the prohibition is a billion times worse for black people.”

Republicans once presented a united front in supporting the war on drugs. That wall began to crumble with the rise of the Ron Paul libertarians. When the House voted 219 to 189 last year to stop the federal ban on medical marijuana in states making it legal, 10 Republicans joined the “yes” side.

Pushing the “no” votes were police employed by the war and private businesses running prisons. They have an economic interest in keeping prohibition in place. It’s about “money and money,” Wooldridge says.

But also about “emotion.” Nearly every police officer had a colleague killed in the drug war. They don’t want to think their friends died for nothing.

Example: In the fall of 2012, two deputies flying over southeast Colorado to locate the marijuana harvest died when their light plane crashed. Two months later, Colorado legalized recreational pot.

The war on drugs, especially marijuana, is clearly entering its twilight phase. The question now is, How many million more American lives are going to be ruined and how many billion more dollars will be poured down the drain before we recognize its futility and move on?

Froma Harrop is a syndicated columnist. Follow her on Twitter @FromaHarrop. She can be reached by email at: fharrop@gmail.com.