For posting:
- invitations to games (you can also use the New Game menu)
- information about upcoming tournaments
- discussion of games (please limit this to completed games or discussion on how a game has arrived at a certain position ... speculation on who has an advantage or the benefits of potential moves is not permitted)
- links to interesting related sites (non-promotional)
Another reason why this should not be allowed:
A "move" is not the action of a piece travelling, but the action of putting a piece on a free square (or occupied by opponent, but that doesn't apply here). Since a5 is occupied, the R can't move there