The recent letter that 47 Republican Senators sent to Iran concerning President Obama’s authority to negotiate has a distant echo in events leading up to the Congress of Westphalia. At the Diet of Regensburg in 1641-42, Imperial estates were disappointed with Emperor Ferdinand III’s unwillingness to accept negotiations with France and Sweden to end the war. While they pressured him to accept the Treaty of Hamburg (1641), which established the framework for a peace conference, they also took direct action by writing to the governments of France and Sweden. Their purpose was to encourage the foreign powers to make peace, at least in part by signalling the willingness of Imperial estates to negotiate, regardless of whether the Emperor seemed to be equally well disposed.
The two events, historical and contemporary, both have their roots in a government where power is shared among different branches. The Emperor had long claimed exclusive authority to conduct foreign policy, but the estates also insisted that they had an advisory role, much as the United States’ Senate must give its advice and consent before a foreign treaty can become law. While no one disputes that the Senate has this role in the United States, it is uncertain whether the letter crosses into the president’s domain of conducting negotiations. The letter also addresses the distinction between an executive agreement, which can be made without the Senate’s consent but which lacks the force of law, and a duly ratified treaty.
One distinction between the events of 1642 and 2015 is that the Imperial Diet wrote in its official capacity as a body representing the Empire. The Republicans’ letter was sent by individual members of the Senate and not in the form of an official act.