They can do it right now, today, if they so choose. Whether it's a trade agreement or not, if they want to devalue their currency to make themselves competitive on the global stage, if they're going to go down that avenue, what do you do? The IMF has policies in place, but that's basically all you have. Whether it's in a trade agreement or not is irrelevant, because they can still do it in or out of a trade agreement.
On May 12th, 2016. See this statement in context.