This follow-up to a previous report provides documentation concerning the status of a pinned knight. http://www.nationmaster.com/encyclopedia/Pin-(chess)

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What steps will reproduce the problem?
1. White's King is opposed by Black Rook, and White's Knight is protecting
the White King from check. White's Knight is at the moment, pinned. (see
documentation, below)
2.White's Bishop captures Black pawn and checks Black King. 
3.Black King attempts to capture the White Bishop because the White Knight
is pinned.  

What is the expected output? What do you see instead?

Black King may capture White Bishop.
PyChess prevents this legal move.

Does it happen every time?

Game situation has not reoccurred, but I would suppose so.

What version of the product are you using?

Reported previously, Philidor (0.8.2, I believe)

Did you use an installed version of PyChess or did you run in from a
tarball/svn?

Installed by Add/Remove

Please provide any additional information below.

Please attach the latest pychess logfile.
For PyChess <= 0.6.x it's hidden in your homedirectory and called
".pychess.log".
For PyChess > 0.6.x, it's in a hidden folder, under your homedirectory,
named ".pychess/"

DOCUMENTATION:
from:
http://www.nationmaster.com/encyclopedia/Pin-(chess)

In chess, a pin is a situation in which a piece is forced to stay put
because moving it would expose a more valuable piece behind it to capture.
In effect, pinned pieces are blocking a check on a king or blocking an
attack on a more valuable piece. Listen to this article · (info) This
audio file was created from an article revision dated 2006-03-08, and does
not reflect subsequent edits to the article. ...  The word check has these
meanings: In finance, a cheque (spelt check in American English) is an
order for transfer of money. ...  The king (♔♚) is the most 
important
piece in the game of chess. ...

In the diagram to the right, the black knight is pinned to the black king
by the white bishop. This is an absolute pin, because the rules forbid
moving the knight, as it would expose the king to attack.

Thanks

Original issue reported on code.google.com by 2leewar...@gmail.com on 1 Jan 2009 at 1:28

Attachments:

• [Black's move](https://storage.googleapis.com/google-code-attachments/pychess/issue-365/comment-0/Black's move)

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Please see the referenced documentation from the same web page as above, please
particularly see the last sentence, it would support your position it would 
seem. I
would suggest, at this point, to go with established international play rather 
than
various arguments. Hopefully such a consensus exists.

http://www.nationmaster.com/encyclopedia/Pin-(chess)

Although the chess tactics article does not specifically categorize pins as 
tactics,
they are useful in tactical situations. One tactic which takes advantage of a 
pin can
be called working the pin. In this tactic, other pieces from the pinning 
piece's side
attack the opposing pinned piece. Since the pinned piece cannot move out of the 
line
of attack, the pinned piece's player may move other pieces to defend the pinned
piece, but the pinning player may yet attack with even more pieces, etc. 
Pinning can
also be used in combination with other tactics. For example, a piece can be 
pinned to
prevent it from moving to attack, or a defending piece can be pinned as part of
tactic undermining an opponent's defense. A pinned piece can no longer be 
counted on
as a defender of another friendly piece (that is out of the pinning line of 
attack)
or as an attacker of an opposing piece (out of the pinning line). However, a 
pinned
piece can still check the opposing king.

Original comment by 2leewar...@gmail.com on 1 Jan 2009 at 1:57

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http://www.fide.com/info/handbook?id=124&view=article
Please read 3.9!

Original comment by gbtami on 1 Jan 2009 at 8:05

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Original comment by gbtami on 1 Jan 2009 at 8:06

• Changed state: Invalid