I was playing a chess game with a friend of mine, and we came to the following position:



Now, it was white's turn (I was white). I figured I would move my queen to C8 and check black (note that we are both novice players, so maybe there would be an even better move than the one I was planning here. My question however relates to this specific move). My friend subsequently moved his black queen to C1, checkmating me.

I argued that this move was illegal, because I had checked him and therefore he was obliged to make a move that would make sure his king was not in check anymore.
He argued that this was not true, because a chess game ends with checkmate. Hence, he did not need to 'uncheck' his king because he could end the game with a checkmate.

I looked at the official FIDE rules, but we couldn't find and exclusive answer. Does anyone know who was right, my friend or I?

You are correct. A player in check must deal with the check

JWhis and you are correct. Here's a way to think about it:

Remember that the modern (Western) version of the game evolved in the Middle Ages in Europe, and monarchs got very touchy about games where the king got killed as a victory condition. Sends all the wrong sorts of symbolic messages, you know? Since capturing and ransoming nobility (occasionally even kings) after a battle was common practice, the idea of stopping the game a move short of the actual killing of the king (allowing him to be gracefully, if expensively, ransomed later off stage...) helped royal heads to sleep better at night and kept commoner heads attached to their bodies.

So by that logic, in your game who would actually capture/kill the other guy's king first? White of course, since if 1. Qc8+ Qd1+ 2. Qxe8 captures the king first. Make sense?

BTW, there is a rule to that effect in the FIDE rules and you just missed it... I don't know where it is, but it *MUST* be there...

Qc1 isn't even mate anyway!

No, but if it were Black to move in the diagramed position, then 1... Qd1# would be... Probably just a typo in the original post, but it's funny how everyone missed it until now!

I saw it but I just assumed he meant Qd1. In dubio pro reo.

Everybody thanks for the replies;
Hitchhiker and Wildman, we did find that rule but weren't sure if this would still be the case if the opponent could checkmate. Thanks for your answer!

About the last move: you are right, I made a typo. It was supposed to say Qd1, like hitchhiker said

If there were an exception for checkmate it would be mentioned in the rules, you can take rules like that at face value. No exceptions listed means there are no exceptions.