House rules

@22

Yes, some people use house rules: stalemate = win, 2 pawns 1 square instead of 1 pawn 2 squares, takebacks, a win if a king reaches the 8th rank etc. It leads to endless and useless disputes.

Chess.com also does not correctly implement the Laws of Chess, and that is unfortunate.
'0.2 It is recommended that competitive games not rated by FIDE be played according to the FIDE Laws of Chess.'
Chess.com pretends to offer competitive games, but does not completely follow the recommendation.
Chess.com breaks the following Laws of Chess:

• 0.2
• 1.5
• 5.1.2
• 5.2.2
• 6.3.2
• 6.7.1
• 6.9
• A.1
• B.1

tygxc: Thanks for the link to the Laws of Chess:

3.9.2 No piece can be moved that will either expose the king of the same colour to check or leave that king in check.

There it is..

As for chess.com the computer won't let you make an illegal move. But for OTB w/ the nextdoor neighbor, making an illegal move basically is a get-out-of-jail-free card. Plus there are two kinds of illegal moves: (1) a stupid blunder [and leaving your King in check is worse than leaving your Queen hanging], in which case you deserve to lose; or (2) outright cheating, like moving your Knight 3 diagonal squares, in which case you get a take-back for CHEATING?

tbqh, I did pull that move on the neighbor guy last month: Knight 3 diagonal squares & forked his Rook & King. He immediately resigned. But I figure that's a case where if he's too stupid to catch the cheating, then he deserves to lose....

If you want to play casual games with your neighbor with whatever house rules you decide on then no governing body will stop you. If you try using your non-standard house rules in a rated OTB tournament then the TD/arbiter will correct you. Deliberately playing an illegal move in a rated game is unethical and might result in penalties ranging from a warning to loss of game or even to an ethics complaint to get you suspended from OTB chess. That is in addition to the time adjustment made to the clocks to penalize any illegal move (well, a game-ending penalty would eliminate any need to adjust the clocks).