Iran’s relations with international media have improved considerably since the election of Hassan Rouhani as president and the beginning of serious talks over its nuclear program. More Western journalists have been allowed to visit the country, Rouhani and Foreign Minister Mohammad Javad Zarif have given numerous interviews to Western journalists and U.S. newspapers have featured their op-eds.

The enhanced interchange is one reason the detention of The Washington Post’s correspondent in Tehran, Jason Rezaian, is so unwarranted. Rezaian, a dual U.S.-Iranian citizen, and his wife, Yeganeh Salehi, who is also a journalist, were arrested at their home a week ago Tuesday.

Since then, their families and The Post have not heard from them, though an Iranian judicial official confirmed Friday that they were in government custody. Two U.S. citizens working as freelance photographers are also being held. No charges have been brought, and the detainees apparently have had no access to legal counsel. Their whereabouts are unknown.

When Rezaian was arrested, he had just returned from covering the latest round of negotiations in Vienna over Iran’s nuclear program, where the two sides reported progress and agreed to a four-month extension.

Rezaian told Post videojournalists last year that he had observed that both Iranians and Americans wanted “some sort of end to this standoff over Iran’s nuclear program” because “at the end of the day there are many more issues of shared importance … that these two countries need to talk about.” That pretty well sums up the argument Rouhani has advanced since his election.

Rezaian’s arrest silences a reporter who was dedicated to fairly explaining Iran to U.S. readers. It also raises questions about whether Rouhani’s professed policy of “constructive engagement” is still in effect. Tehran could quickly and easily silence these doubts by unconditionally releasing Rezaian, Salehi and the other Americans.