I agree that the rule should be clearly posted. Cheating of this nature is forbidden by the terms of service. Although I do not think it takes much interpretation to arrive at that conclusion, it is not explicitly defined. I have been working on publishing a new set of game rules, but they are (self-evidently) not currently public.
I was lenient in this case because clarification of the rules in light of the game mechanics changes are not yet posted in a pinned thread (although a person who was unsure of the legality of this behavior could find it in this forum with a minimum of effort). Nonetheless, I cannot allow players to benefit from this mass cheating to the detriment of rule-abiding players. Applying in-game warns is an effective method of delivering the message to players who do not read the forums. These warnings cause no harm to your nation and will expire in 90 days. If you elect to cheat after receiving this clear message then you will lose your nation. If you don't, you will suffer no ill effect.