In almost every game I've come across that includes a dark situation designed to change the way a user interacts with the environment, there are always some players who turn up their monitor's gamma correction in order to negate the desired effect.

Is there a way to prevent users from adjusting their gamma correction to 'cheat' their way out of a challenge? (the darkness)

I'd imagine if you could reliably retrieve the current gamma correction of the user's monitor, you could use that to more or less prevent the advantage it would otherwise grant without causing the normal users any inconvenience.