`  :This answer comes from Yasser Seirawan himself: :No.  At no time can a player leave his King in check, even for a ``half a move``.   Example: Black's last move is 1...Rc1+.  The White player cannot play 2.Kf1/Ed1.  The White player could play 2.Ke2/Ee1 but cannot have exposed his King to the Rook check for ``half a move.``   `