Shadowing is a special kind of battle avoidance open to cavalry
armies only (18.2). The rules for avoiding battle (when and where
it may happen) apply, and the die roll needed is the same.
If I'm not incorrect, there is one exception to the case:
You may not shadow into a space with an enemy stronghold
under any circumstances.
I think this could have been also said in 12.4.
Don't take this as a rant or anything. It's just that if you have forgetten how the rules go, you will go to 12.4, see the avoid battle rules and miss the exception mentioned in 17.1. I can't remember if there some similar scatter in the rules. Otherwise, quite clearly organized and well-written rules. Index would have been great but the table of contents is good, so it helps a lot.