Can someone point out where in the core rules or the FAQ it defines control? After reading over the FAQ, I found

FAQ p8

Triggered Abilities: Any ability on a card in
play that begins with "Phase:" or "Response:"
is a triggered ability. These abilities are
optional, and must be triggered by the player
controlling the card at the appropriate time
for their effect(s) to occur. An example of a
triggered ability is the Dominance: effect on
Cersei Lannister (CORE L39).

FAQ p15

3) Trigger a card effect printed on one of the
character, location, or attachment cards y ou
control in play (or, in rare circumstances, from
out of play).

When looking at Trident Reinforcements (Core),

Dominance: Return Trident Reinforcements from your dead pile to your hand. Use this ability if there are at least 3 characters in your dead pile.

For you to trigger this ability you still have to control him right? So even though he is'nt "in play" you do still control him? The real question here is Do you still control characters in your dead pile?

You control all cards you own unless an effect says otherwise. This is the conclusion that can be drawn from the definition of "own" in the FAQ.

So this does include cards in your dead and discard pile as well?

Dimnos said:

"A card a player owns is a card he or she brought to the game in his or her deck"

You own the cards in your dead and discard pile (and your hand, and your deck), so you "control" those cards as well.

Ok. So if you play Xaro Xoan Daxos (Core)

"After you play Xaro Xoan Daxos from your hand, choose and return a character you control to its owner's hand."

Could you return a character from your dead or discard pile?

Although I'm not able to find an FAQ section about this, the answer to your question is no. Card effects cannot target out-of-play states, such as your draw deck, dead pile or discard pile, unless they specifically state such as part of thier effect. Various plots and event cards are worded this way, such as Summoning Season […search your deck for a character…] or Dance with Dragons […search your deck for a Dragon card…] . So even though you own/control all of your cards, from the game's perspective, they are not under your control unless they are in the play area, i.e. marshalled or put into play.

Ktom will likely followup, perhaps with the actual reference.

(3.13) Out of Play States
In general, card effects on non-event
cards in a player's hand, deck, shadows area,
discard pile, and dead pile are not considered
to be actionable unless the card specifically
states that it can be triggered while in its outof-
play state.

"Out-of-play cards are not actionable unless specifically stated" includes not only using the abilities/effects of the card itself, but also using the abilities/effects of other cards on the out-of-play card.

Bam! That is exactly what I needed. Thank you sirs.