From: "J. Andrew Lipscomb" <ewwa <at> CHATTANOOGA <dot> NET>
Date: 14 apr 2000
Subject: Re: Checkmate

> Illegal moves:
>   (1)A move is illegal to make a double pawn.
>   (2)A move is illegal to make a deadlocked piece.
>   (3)A move is illegal for a player if his King's square is attacked by an
>      opponent piece after the move.[to remain in check, to move into check
>      or to expose the king to check]
>   (4)A move is illegal to make a repetition check move [Mr.  Horiguchi
>      wrote in an addendum the following clarification: "... In the event
>      of perpetual check, if one player player does it FOUR TIMES(three
>      times is permitted), he will lose his game".
>   (5)A move is illegal to make a dropping check move by a pawn which leads
>      to a position in checkmate at once(dropped-pawn mate).
>
> Legal moves:
>
>   A legal move for a player is a move to leave the check by moving pieces
>   on the board or by dropping if his king is in check. Otherwise, a legal
>   move by a piece on the board which can go[move] or a drop move, which is
>   not illegal.

The Renmei's website (English version) also does not list leaving the
king in
check as an illegal move.  So we have the answer on that question.  But it
also states that checkmate (but *not* what Western-chess calls
stalemate) ends
the game.

(On another issue, it indicates that when you remove your hand from a piece,
the move is completed.)