[Retros] Are the King and the Rook pieces or what?

[raosorio at fibertel.com.ar]

Dear retrofirends,

Many thanks for the clever discussions on this point. These are very useful to
clarify my mind in the project which I'm involved toghether with Sergio Orce and
Jorge Lois (Peña del Mate de Ayuda, Argentine Chess Club).

this project would be to define "Minimal Deviation from the Rules" (MDR) as an extended 
space for compositions where a last (and just last ) illegal move in the diagram is 
accepted. This illegal move would be of MDR type (say, geometrically correct) and 
the problems would create puzzles and paradoxes to find that move and its consequences.
all the above strcictly contained in the CODE.

A furhter question on the castling case. I the wK is standing on e1 and a wR on h1, castling
is legal and posible but the player conducing the white side moves the King to g1 and that's
it, he stops there. This move is illegal, but it's also a half legal move. Is white forced to move
the king freely or he's forced to castle?

Best,
Roberto