A bedrock principle of international law is that borders can't be changed by force. Governments cannot be rewarded for action that comes at the expense of another's territory, and there is no time limit on such behavior, no point at which the world can acquiesce. That is why U.S. President Donald Trump's tweet last week endorsing Israel's claim to sovereignty over the Golan Heights, territory seized from Syria 52 years ago, was so shocking. Trump's decision looks more like domestic politics than realpolitik and validates criticism of a U.S. decision-making process that is haphazard, ad hoc and detrimental to its national interest.

Israel took the Golan Heights, a 1,200 sq-km plateau, from Syria during the six-day Israeli-Arab war in 1967. Successive Israeli governments have argued for retention of it because of its strategic value: It provides line of sight over much of Syria — the suburbs of Damascus are visible from there — as well as access to the Sea of Galilee, a critical source of water for the region. Some 20,000 Israelis have settled in the area since it was taken by Israel; a similar number of Druze, Syrian Christians also reside there. Israel passed legislation annexing the territory, but the rest of the world has not recognized the law.

Officially the move is intended to strengthen Israel's security. There has been an influx of anti-Israel forces such as Hezbollah or other militaries supported by Iran into southwestern Syria. U.S. National Security Advisor John Bolton explained that allowing the Golan Heights "to be controlled by the likes of the Syrian or Iranian regimes would turn a blind eye to the atrocities of Assad and the destabilizing presence of Iran in the region." As Trump tweeted, the Golan Heights are "of critical strategic and security importance" to Israel.