Is it required to be of sound body and mind to contract?

I don’t have one. Ability to understand the consequences of your actions?

Even if she explicitly “agreed” to it, it doesn’t matter because she’s been roofied!

What if government A force fed the population of Ruritania with mind-altering drugs and glued their eyes open to watch pro-state propoganda, and after government A packed up and moved to an island in the middle of the Pacific, every citizen signed a contract to establish the new government B? Everyone would have “agreed” to this state, and so long as the effects of the drugs from government A stayed in their systems, government B would be a completely voluntary state – IF Lorraine’s explicit “yes” means she wasn’t raped.