The truck dispute between Mexico and the US is a big deal in the making - perhaps the first battle of a global trade war? Or the shock to the system that convinces everyone there has to be a better way?
It does look as if the US is in the wrong - if you go by the rules - and President Obama is faced with a choice: persuade Congress to comply with the rules or give up on a key aspect of NAFTA, following through on a campaign threat that most people thought was hollow but which has some continuing political advantages.
There is some political cost in the White House forcing Congress to reinstate the truck scheme - at a time when the Obama team want to reduce the spending of capital in order to keep some for future rainy days. Result: the trucks won't roll.