The Geneva Convention is a unique decision for 
Switzerland. It should not be confused with the decision Sign the Geneva Convention although they are related. Switzerland decides to host the convention, where the famous Geneva Conventions, international laws for warfare was introduced.
It opens the possibility for all civilized countries to take the decision Sign the Geneva Convention.
It requires that Switzerland owns Geneva (ID 607) and that any great power has a War exhaustion of at least five. It gives Switzerland 10 prestige, as well as signing the actual convention. Unlike all other nations, it is actually not a requirement, that Switzerland has less than 25 infamy. Signing the convention gives 0.01 infamy pr. month, but lowers war exhaustion by 0.02 pr. month and gives 5% army organisation regain rate for the rest of the game.
The monthly infamy adds up to 1.2 infamy pr. decade, so it is well worth it to take the decision.