Print[StringJoin[
   RandomChoice[
    Select[Union[
      Permutations[{"\[WhiteKing]", "\[WhiteQueen]", "\[WhiteRook]",
        "\[WhiteRook]", "\[WhiteBishop]", "\[WhiteBishop]",
        "\[WhiteKnight]", "\[WhiteKnight]"}]],
     MatchQ[#, {___, "\[WhiteRook]", ___, "\[WhiteKing]", ___,
         "\[WhiteRook]", ___}] &&
       OddQ[Subtract @@ Flatten[Position[#, "\[WhiteBishop]"]]] &]]]];