As I understand it, the Lao government did follow the legal obligations required to them through the Mekong River Commission framework - regarding procedure and time. The legal obligation of Prior Notification, etc. should be called into question and reworked if the outcome is so ambiguous and upsetting to parties involved.
Also, according to the current studies of the dam impacts, there is no significant transboundary impact. The truth is, that the things people are focused on may not have impact, but there are always unknowns that even the most astute scientists miss, and the most adept engineers cannot plan for.
Learn by doing seems to be the motto of the day. Now, what can the international community offer by way of mitigation in the face of development realities? There is a bargaining chip that no one is playing. If you are one of those people who can negotiate for the river, please think long and hard about this opportunity.