Arms-con­trol en­thu­si­asts must be dis­ap­point­ed. On Thurs­day af­ter­noon, Pres­i­dent Don­ald Trump cut short his sum­mit in Ha­noi with North Korea’s Kim Jong Un. “Some­times you have to walk,” Trump ex­plained later at a news con­fer­ence.

He’s right. Trump said Kim de­mand­ed a full lift­ing of sanc­tions in ex­change for only par­tial de­nu­cle­ar­i­za­tion. It’s an old tac­tic for the North Ko­reans. They ne­go­ti­ate, pock­et con­ces­sions, then fail to de­liv­er.

Un­for­tu­nate­ly, the pres­i­dent is wrong a­bout an­oth­er point he made at the news con­fer­ence: the pros­pects for a deal with Kim. As Trump tells it, Kim would like for his gulag state to be pros­per­ous like Viet­nam — an­oth­er form­er U.S. foe with a pen­chant for Marx­ism. “I’ve been tell­ing ev­er­y­bod­y, they have tre­men­dous po­ten­tial,” Trump said, re­fer­ring to North Korea.

They don’t. It’s hard to know what’s going on in­side Kim’s head, but if he has an ounce of com­mon sense he must know that he can­not both over­see a heal­thy mar­ket ec­on­omy and re­main the war­den of a pris­on state.

This is not to say that au­thor­i­tar­i­an states can­not be­come weal­thi­er; China and Rus­sia show they can. But the North Ko­re­an state is a com­bi­na­tion of Josef Sta­lin’s Soviet Union and George Or­well’s “1984.”

Start with the fact that slav­er­y re­mains a key part of its ec­on­omy. Mat­thew Zweig, an an­a­lyst for the Foundation for Defense of De­moc­ra­cies, es­ti­mates that one in 10 North Ko­re­an work­ers are slaves, pressed into la­bor in camps vis­i­ble in sat­el­lite photos.

There are also ap­prox­i­mate­ly 100,000 North Ko­reans sent a­broad to work main­ly as man­u­al laborers, whose earn­ings are taxed at near con­fis­ca­tory rates. (Much of this is de­tailed in a law­suit filed by a North Ko­re­an ship work­er who worked 12-hour days at a ship­yard in Po­land in un­safe con­di­tions with al­most all of his wages paid in tax­es to Pyong­yang.) It’s a scheme that pro­vides Kim’s re­gime with the hard cur­ren­cy it needs to build nu­clear weapons and the mis­siles to de­liv­er them.

It should go with­out say­ing that this sys­tem will nev­er yield the kind of heal­thy ec­on­omy that Trump dreams of for North Korea. For North Korea to be pros­per­ous, its cit­i­zens can­not live in per­petu­al ter­ror and fear. The prob­lem for Kim is that, with­out fear, his re­gime would crum­ble.

For now, then, it doesn’t look like an eco­nom­ic rev­o­lu­tion is on the ho­ri­zon. Trump’s in­stinct to try to ne­go­ti­ate a deal to at least defang this men­ace is not crazy. But his of­fer to make North Korea pros­per­ous is fool­ish.

As he con­tinues to deal with North Korea, Trump would do well to study Ron­ald Rea­gan’s presi­den­cy. Like Trump, Rea­gan sought a deal with a dic­ta­tor. But Rea­gan’s leg­acy is not the arms-con­trol a­gree­ment he made with Soviet lead­er Mikhail Gor­ba­chev. It is the mo­ral clar­i­ty Rea­gan brought to America’s re­la­tion­ship with the coun­try he called an evil em­pire — a vi­sion that helped to has­ten its col­lapse.

It’s a mod­el Trump seems to be fol­low­ing in Ven­e­zue­la, where he has a chance to help the Ven­e­zue­lan peo­ple usher out Nic­o­las Maduro, the Western Hemisphere’s se­cond-worst ty­rant. Trump de­cid­ed not to sign an a­gree­ment with Kim be­cause “we just felt it wasn’t ap­pro­pri­ate, and we re­al­ly want to do it right,” he said just be­fore leav­ing Ha­noi. If the pres­i­dent is look­ing for a for­eign pol­icy leg­acy, his best chance is half a world away.