Edicts are landscape-shaped cards that introduce straight-up rule changes. Unlike Events and Projects they don't need to be bought, and apply to all players. They are similar to Landmarks, but in order to ensure that they could not be a Landmark instead, one of the rules this week will be that Edicts should not be tied to VP-scoring.
It's a simple enough concept, but I think the tricky part will be coming up with an Edict that wouldn't be better off as an Event or Project, and to come up with something that is subtle enough to maintain the essence of Dominion but meaningful enough to offer a fun and varied gameplay experience.
Looking at some of the submissions so far, it does seem a bit difficult to design an Edict that wouldn't be better served as a Project or Event (or at least couldn't easily be turned into one):
* Haggling, with its overpay, is effectively an opportunity cost like an Event (though the recommended change by grrgrrgrr doesn't fully capture the original design intent, but it could be modified a bit).
* Smelting could very easily be a Project (even a 0-cost one, but could also probably work at $2 or $3).
* Progress, being optional, could also be a Project.
The opportunity cost to turn an Edict into a 0-cost Project is one missed Buy, which is very minimal.
To me, Monarchy and Lucky Find fit the Edict type well. They are mandatory changes that happen (and I can see the change happening in many Edicts during Setup, such as Lucky Find). If Monarchy changed to a Project, you could choose when to start using it (if at all), which would totally change its purpose - as an Edict, it changes your game.
And with those thoughts, I submit...

The game does not end with 3 empty Supply piles, but with 5.
Setup: for each Kingdom Supply pile, use only half as many of each uniquely named card as usual (rounded up).
My starting thought for this was to use smaller Supply piles (possibly all, including things like Gold, Curses, etc.). Or for Kingdome piles, maybe it would even scale per player (2 cards of each type per player, so 2-player games would have 4 cards per pile, 3-player with 6, 4-player with

... but then what would I do with things like Knights, Castles, etc.? But with smaller piles, the game would end very quickly on 3-piles, significantly changing the game and the chance to develop big turns later in the game. So it made sense to turn a 3-pile ending in something bigger - I figured 5 was a good number.
I could make the Edict a bit wordier, noting that a game ending by "pile-out" now requires 2 additional piles, to let Rationing scale up to 5 or 6 players, but I think that could be addressed in a rulebook for it, rather than on the card. It is already wordy enough, to account for various Kingdom piles, like Split Piles (which would now by 3-3 instead of 5-5), Knights (which would remain unchanged), and Castles (which would only use the 8 unique cards, even in a 3- or 4-player game).