Suppose, for example, a player's Bishop is pinned (say, between his own
King and an opposing Rook). The Bishop thus cannot move, and
essentially it projects no power while it is pinned.

Can the opposing King move onto the pinned Bishop's diagonal?

Or, suppose a player blocks a check by moving his Knight (so the Knight
is pinned), but the Knight's new position (in theory) exerts power onto
a square occupied by the opposing King. Is the opponent in check?

My instinct tells me that a pinned piece cannot cause check, because it
could not actually play a part in the capture of the King. If the
piece becomes un-pinned (the player moves the king, etc) then it could
immediately place the opponent in check. But that's a guess...

Can anybody tell me the actual rule? Thanks!

--
David Filmer (http://DavidFilmer.com)