Anything that's sensible or thoughtful can be described as reasoned. A reasoned decision about which candidate to vote for requires some research and careful thought.
You probably assume that most rulings made by judges are reasoned — they're logical and intelligent. If you have a friend who tends to act in an irrational or foolish way when he's upset, you also assume that in certain circumstances his decisions won't be reasoned. The adjective reasoned comes from reason, from the Old French raisoner, "speak, discuss, or argue."