Correction: An earlier version of this editorial incorrectly referred to Bahrain’s Shiite population as a minority. Shiites are the majority sect in the country. It also incorrectly attributed reporting to the Daily Beast instead of Bloomberg View.This version has been corrected.

A small group of Bahraini women carry national flags and a banner showing jailed Shiite cleric Sheikh Ali Salman during a protest against his conviction of insulting the Interior Minister in Manama, Bahrain, Tuesday, June 16, 2015. (Hasan Jamali/AP)

GOVERNMENTS ACROSS the Middle East perceive that President Obama has subordinated much of U.S. policy in the region to the goal of completing a nuclear bargain with Iran. Policies that might disturb Tehran, such as acting against the Syrian regime of Bashar al-Assad, have been put on hold; meanwhile, traditional U.S. allies that are skeptical of the deal, such as Saudi Arabia, have been promised stepped-up U.S. military assistance.

One U.S. client that has sized up the situation with particular cynicism is Bahrain, a Sunni monarchy in the Persian Gulf that hosts the U.S. Fifth Fleet. Since 2011, the regime has been harshly repressing opponents calling for greater political representation for the country’s Shiite majority. Regular demonstrations in Shiite areas are put down by force; activists are arrested and often tortured; and opposition politicians and human rights monitors are prosecuted on trumped-up charges. In response to sporadic criticism and pressure from the Obama administration, the regime has occasionally promised reforms or dialogue with the opposition but invariably has failed to follow through.

More recently, the ruling al-Khalifa family appears to have concluded that it can afford to flout the Obama administration openly. Last year it expelled the visiting State Department assistant secretary for human rights after he met with opposition members, including from the al-Wefaq party. In December, it arrested the head of the party, Sheikh Ali Salman. On Tuesday, a court sentenced Mr. Salman to four years in prison on flimsy charges of “inciting hatred” and “insulting public institutions.”

King Hamad bin Isa al-Khalifa attended a horse show in England rather than the summit Mr. Obama held to sell the Iran deal to Persian Gulf leaders. But he’s still counting on a handsome payoff: U.S. tolerance for the imprisonment of the country’s foremost opposition leader, and more military aid to boot. If that sounds like chutzpah, the king has been encouraged: According to Bloomberg View, Secretary of State John F. Kerry promised Bahrain’s foreign minister last month that the administration would work to lift a partial ban on arms sales to the island state, imposed four years ago in reaction to the repression.

While some U.S. military supplies to Bahrain have continued all along, items that could be used in the domestic crackdown, such as Humvees, ammunition and tear gas, have been held up. Mr. Kerry’s pledge came before the case of Mr. Salman — whose arrest the State Department had protested — had been disposed of, and, according to the Bloomberg View report, before a U.S. inter-agency decision to end the ban had been made.

The State Department issued a statement on Tuesday saying the administration was “deeply concerned” about Mr. Salman’s imprisonment. It should be. As Brian Dooley of Human Rights First observed, the verdict “drives Bahrain deeper into political crisis and sweeps any chance of a negotiated settlement off the table” while encouraging “those seeking violent change.” That’s a problem Mr. Obama seems to understand; in an interview with the New York Times in April, he observed that “the biggest threats that” Persian Gulf states face “may not be coming from Iran invading” but “from dissatisfaction inside their own countries.” In the case of Bahrain, he’s surely right. But in its zeal to complete the Iran deal, the administration seems to be setting aside the president’s wisdom.