Samantha Power, the U.S. ambassador to the United Nations, speaks to reporters. (Seth Wenig/Associated Press)

PRESIDENT OBAMA’S decision to abstain on a U.N. Security Council resolution condemning Israeli settlements reverses decades of practice by both Democratic and Republican presidents. The United States vetoed past resolutions on the grounds that they unreasonably singled out Jewish communities in occupied territories as an obstacle to Middle East peace, and that U.N. action was more likely to impede than advance negotiations between Israelis and Palestinians.

The measure, approved 14 to 0 by the Security Council Friday, is subject to the same criticism: It will encourage Palestinians to pursue more international sanctions against Israel rather than seriously consider the concessions necessary for statehood, and it will give a boost to the international boycott and divestment movement against the Jewish state, which has become a rallying cause for anti-Zionists. At the same time, it will almost certainly not stop Israeli construction in the West Bank, much less in East Jerusalem, where Jewish housing was also deemed by the resolution to be “a flagrant violation under international law.”

By abstaining, the administration did not explicitly support that position, which has not been U.S. policy since the Carter administration. In explaining the vote, U.S. Ambassador Samantha Power pointed out that the council was sanctioning Israel even while failing to take action to stop a potential genocide in South Sudan or the slaughter in Aleppo, Syria. Yet in failing to veto the measure, the Obama administration set itself apart both from previous administrations and from the incoming presidency of Donald Trump, who spoke out strongly against the resolution.

A lame-duck White House may feel a radical change in policy is justified by Israel’s shift to the right under Prime Minister Benjamin Netanyahu; Israel’s governing coalition is supporting legislation that would legalize dozens of settlements that Israel itself defines as illegal, because they were constructed on private Palestinian property. Mr. Netanyahu supported a partial settlement freeze for 10 months in 2009 and 2010 at Mr. Obama’s behest, but has since allowed construction, including in some areas deep in the West Bank.

Nevertheless, settlements do not explain the administration’s repeated failures to broker an Israeli-Palestinian peace. The Palestinian Authority under Mahmoud Abbas proved unwilling to negotiate seriously even during the settlement freeze, and it refused to accept a framework for negotiations painstakingly drawn up by Secretary of State John F. Kerry in 2014. In past negotiations, both sides have acknowledged that any deal will involve the annexation by Israel of settlements near its borders, where most of the current construction takes place — something the U.N. resolution, which was pressed by the Palestinians, did not acknowledge or take into account.

Israeli officials charged that the abstention represented a vindictive parting shot by Mr. Obama at Mr. Netanyahu, with whom he has feuded more bitterly than he did with most U.S. adversaries. The vote could also be seen as an attempt to preempt Mr. Trump, who appears ready to shift U.S. policy to the opposite extreme after naming a militant advocate of the settlements as his ambassador to Israel. Whatever the motivation, Mr. Obama’s gesture is likely to do more harm than good.