Where was the first Social Contract proposed in a rule book?

Question

We have questions delving on the social contract themselves and what it is (like What is a social contract?), and there is also explained where the word comes from. We know very well that most RPGs hail to a good degree from wargames via Chainmail.

Wargames, while having quite some explicit rules (sometimes going to managing fuel by the centiliter), also generally have some implicit rules, all in all pretty much the unwritten social contract of the wargame. Some of these of these unsaid rules (actually for almost any game) are "don't interrupt a running game as a bystander" or "don't punch your opponent". More specific to wargames, it is also considered rude to touch the miniatures of your opponent, even if they are removed from the game, yet I have never encountered a rulebook stating this¹. It is just enforced usually.

But when wargames turned into RPGs, a lot of the rules changed. As we explored with the search for Where and when did "the GM is always right" get codified first?, the judge turned into the GM. They changed from an entity that was supposed to be just and not part of the battles and keep the stiff rules corset free of holes into a fellow player that was to keep everybody entertained, themselves included.

With this change of scope, from a competitive game under supervision of a judge to a cooperative game with/against the GM, clearly a change has happened. This change also changed the implicit rules of the games. Some stayed the same. It is still rude to interrupt a running game session as a bystander. It is still out of the social contract to punch your fellow player or the GM. But not all games are the same:

• Paranoia's implicit (and explicit) rules do not only not discourage PVP, they encourage PVP and treason against the group.
• MAID RPG actively encourages players to molest the other players' characters.
• My Life With Master is a game which is not designed to be fun (in fact, the GM is instructed to crush mercilessly all avenues players find to have fun).^{doppelgreener}

As one can see, the social contracts of these games are VERY different, just from pointing out a single thing about the games. But all this diversity must have come from somewhere. The examples are not picked entirely by random: they contain passages that encourage this behavior, actively altering the social contract that underlies gaming as a whole or most RPGs.

So, which product first made an effort to define what is the social contract of this game or provide general rules for expected/accepted behavior at the game table?

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^{1 - Chess for good lord has several rules for touching board pieces. If it's not your turn you may not touch any piece (safe to tip over your king to surrender). It is illegal to change a move once a piece is let go. And then there is touch-move: touching your own figures forces you to move it if legal, unless you announce you place them correctly (j’adoube). Also, you are forced to try to capture the opponent's figure you touched if at all possible. But Chess is no wargame in the traditional sense.}

Answer 1

The earliest roleplaying game publication I'm aware of that included explicit guidance for how the players were to interact with one another is An Introduction to Traveller (1981):

Obnoxious, obstreperous or rude behavior is not conducive to the enjoyment of play. Loud, disruptive players merely irritate everyone concerned. Do not engage in such behavior yourself, and discourage it in others.

By following the above suggestions, even the neophyte Traveller player can have enjoyable sessions almost from the first.

This book predates Paranoia RPG (1984), and predates the popular use of the term "social contract" within roleplaying games.

The original Dungeons & Dragons white box (1974) describes the duties of the "referee" (the term Dungeon Master had not yet arisen), but doesn't actually give any guidance for how the players should interact with one another or behave at the table beyond following the game rules.