President Obama's foreign policy legacy will include significant, if temporary, curbs on Iran's nuclear program — but not the broader detente with the Islamic republic that he hoped for. More and bitter evidence of that came Tuesday, when Tehran announced that two American citizens and a permanent U.S. resident had been sentenced to 10 years in prison on charges of "cooperating with the hostile U.S. government."

Siamak Namazi, 45, a businessman born in Iran, was an advocate of better relations and more trade between the two countries — which is probably the reason he was arrested while visiting the country a year ago. His 80-year-old father, Baquer, a former UNICEF official, was cruelly imprisoned after he traveled to Tehran in February.

The Namazis are not the only dual nationals suffering persecution in Tehran. Nizar Zakka, a Lebanese citizen, permanent U.S. resident and State Department contractor, was detained in September 2015 while attending a conference. Reza "Robin" Shahini, 46, of San Diego was arrested in July. All were reportedly seized by the intelligence service of the Revolutionary Guard, the same force that subjected Post correspondent Jason Rezaian to 18 months of imprisonment before his release in a prisoner swap in January.

The government of Hassan Rouhani, which negotiated the nuclear deal with the Obama administration, is often portrayed as opposed to this de facto hostage-taking. If so, the government appears powerless to prevent it. Instead, officials complain about the relatively slow return of Western investment and trade following the lifting of United Nations sanctions, even as some of those who promote the opening are unjustly imprisoned.

Iranian foreign policy, too, remains unchanged. The regime has dispatched thousands of fighters to Syria to prop up the regime of Bashar Assad and is using Shiite militias to extend its influence across Iraq. It is encouraging Russia's new bid for influence in the Middle East while doing its best to drive out the United States.

In that context, the long sentences handed to the Namazis are grim but unsurprising. The Revolutionary Guard wishes to head off Western investments that might infringe on its own business interests, and it may hope that its prisoners can eventually be exchanged for lucre. Though it was officially part of a separate claims settlement, the Obama administration's delivery of $400 million in cash to the Iranian regime at the time of the release of Rezaian may have whetted the appetites of Tehran's jailers.

The administration, which duly pronounced itself "deeply concerned" by the prison sentences, may face the choice of striking another distasteful deal or leaving office with a notable blemish on its Iran legacy. In the meantime, promoters of Iranian-American understanding such as the younger Namazi would be well advised not to set foot in Tehran.

FROM AN EDITORIAL IN THE WASHINGTON POST