In Emperor Edition, the targeting of Ranged Attacks is not required, so you can perform the action even if you have no legal targets for it. Given that, can you choose to target nothing if there are legal targets available?
Ranged Attack Targeting
A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
In Emperor Edition, the targeting of Ranged Attacks is not required, so you can perform the action even if you have no legal targets for it. Given that, can you choose to target nothing if there are legal targets available?
If a target exists, you must target it. The clause allowing you to not target only applies if there is no legal target; this will allow you to announce the action.
The answer to the question above has been reversed.
Even if there is a legal target for a Ranged Attack, you may choose not to target it. This is because the text which was accidentally omitted from the Rulebook and the CR that specifically says so has now been correctly added to the CR, here (emphasis mine):
Ranged Attack: "In an effect, “Ranged X Attack” (where X is a number known as the strength of the Ranged Attack) is shorthand for “You may target a Follower or a Personality without Followers in the current enemy army. If its Force is equal to or less than X, destroy it.”"