Last Friday, on the eve of Hanukkah and Christmas, Barack Obama stabbed Israel in the front. The departing president refused to veto United Nations Security Council Resolution 2334—a measure ostensibly about Israeli settlement policy, but clearly intended to tip the peace process toward the Palestinians. Its adoption wasn’t pretty. But, sadly, it was predictable.

Mr. Obama’s refusal to use Washington’s veto was more than a graceless parting gesture. Its consequences pose major challenges for American interests. President-elect...