A royal could make a normal step to avoid get out of check on its first move. The royal queen in Cassia Britania could slide out of check. So it doesn't seem this is universally valid. But, it is probably safe to consider it for any initial move that changes the location of a second piece.
A royal could make a normal step to avoid get out of check on its first move. The royal queen in Cassia Britania could slide out of check. So it doesn't seem this is universally valid. But, it is probably safe to consider it for any initial move that changes the location of a second piece.