> The validity of treaties signed under duress on the other hand I think really deserves some questioning.
Historically, a huge number of treaties have been signed under some degree of duress – most peace treaties are only made when one side is clearly winning, but extracting concessions (however painful) from the losing side is more in the winning side's interests than the risk and expense (in blood and treasure) of continuing the war to a complete military victory.
If one took seriously the idea that treaties signed under duress are invalid, the national borders of Europe and North America (among other places) would have to be very different.
Historically, a huge number of treaties have been signed under some degree of duress – most peace treaties are only made when one side is clearly winning, but extracting concessions (however painful) from the losing side is more in the winning side's interests than the risk and expense (in blood and treasure) of continuing the war to a complete military victory.
If one took seriously the idea that treaties signed under duress are invalid, the national borders of Europe and North America (among other places) would have to be very different.