When President Donald Trump decided recently to pull the US out of the Iran nuclear agreement, many of the deal’s opponents justified his action this way: the failure of Trump’s predecessor Barack Obama to ratify the deal means it’s an executive agreement and not a formal treaty, so is therefore easy to withdraw from, writes Thomas Brackett Reed Professor of Government Andrew Rudalevige in the Washington Post political science blog The Monkey Cage.

However, Rudalevige goes on to point out that even if the Iran deal had been ratified into a treaty, Trump could still have pulled out of it, and he wouldn’t have been the first US president to withdraw from a treaty he didn’t like.