In short: can you intentionally decline an ARO in order to utilize Alert? In full: Player A activates a model and moves within ZoC and LoF but outside the front arc of an enemy model. Player B, not trusting their Dodge to succeed against the attacker, wants to decline to ARO in the hopes they survive and utilize Alert to change their facing. Is this allowed, or are they obligated to declare Dodge? The relevant text from "ARO: Automatic Reaction Order": The relevant text from "Alert": Thoughts: the wording on these sections have changed little from N3 to Code One, other than Warning! being replaced with Alert. It seems generally accepted in N3 that models may decline to ARO in order to utilize Warning!, but it is not explicitly mentioned in either system whether intentionally declining an ARO is actually allowable, or whether doing so qualifies you to utilize Alert/Warning!. I suspect the answer here is "you may decline an ARO to use Alert," but I want to make sure.
First, in the circumstances you describe you're much better off declaring Dodge (either way it'd be FTF, just the Change Facing would be at -3 PH). However it's permitted to say "Trooper X does not ARO" when Trooper X gets an opportunity to ARO. Edit: unless you actually meant Warning! not Alert. These are two different things. Did you mean Warning?
They were activated, and had the opportunity to declare any ARO. If they don't, they've forfeited the ability to do anything.
It is explicitly mentioned whether intentionally declining an ARO is allowable. See the Order Expenditure Sequence, for "Declaration of AROs" (Steps 2 and 4): The Reactive Player checks Lines of Fire to the Active Trooper, and declares AROs. Troopers are not forced to declare the AROs, but if a Trooper can declare an ARO and fails to do so, the chance to declare an ARO is lost. That's on page 23 of the Code One PDF. The Order Expenditure Sequence in N3 (http://infinitythewiki.com/en/Order_Expenditure_Sequence ) also says that (and may be stated elsewhere). So, yeah, you do have explicit permission to not take an ARO if you have the opportunity to do so.
However, declining an ARO indicates you were activated by one, which precludes you from using Alert!.
No, that is not a true statement. A trooper is activated by an ARO if it takes one. If you decline your ARO, you still get to use Alert.
In any case, N3 Warning and C1 Alert have more or less the same wording, including that you can't have declared an ARO in order to use them. Per the original poster's question, declining to declare an ARO is sufficient to meet these criteria, otherwise it would be impossible to ever use Alert against a target in ZoC. It's frequently better to declare a Dodge at -3 (or Reset if applicable) in order to get a FtF, but there are definitely times that you're best off just eating the hit and getting a free turn around. It's especially relevant on models with multiple wounds and high defensive stats (armor or mimetism).
I'd like to see a little emphasis on the rules text that this is possible. Just to avoid discussion on the game table. The rules are clear, but the wording under "Alert" is not.