My interpretation: Everyone knows that Justice is blind. With her signature blindfold, scales, and sword, Justice reminds us that there is a balance to things. Simply because we think that something is not right or not fair does not make it so, and she reminds us that we must figuratively blind ourselves to make sure that we are seeing things from an objective point of view. Perhaps finding that objectivity is what you need to do in order to find the answers you seek.
Interpretation in the book: This fae wishes you to understand your power and your responsibility. If you are wondering why you are facing a situation, look to your past actions. If you can see how you brought yourself to this place, you can perhaps find a way to balance your karma. If you are facing a decision of how to behave in a situation, consider the future ramifications. Choose your actions wisely, and carefully make a bed you will be happy to sleep in. – From A Guide to Mystic Faerie Tarot by Barbara Moore.
For me, Justice has always been about pointing out when you need to be objective. The reason Justice is blind is so that she can be objective when facing a decision. I usually find her in spreads where a decision must be made and where it appears that there is bias toward one side or the other.