I apologize in advance if this has been discussed previously, the search feature gives me a 404 whenever I use it.
I'm interested in knowing if there is anything specific regarding the ownership of decklists after an event. From what I have found, decklists are to be sorted and “filed”. From communication with others it seems that the TO is responsible for the filing of and ownership of decklists, but having access to the decklists as a judge seems to be a privilege that could be abused. Let me explain further.
This Monday I was the head judge for a Standard constructed GPT for Toronto. This event also grants byes for a local Comp. REL tournament that is to be held this Saturday. While I will not be judging the event this Saturday, I as a player expect to see many of these same decks being piloted by the very players to whom the decklists from Monday's event are tied. It is not clear to me, both officially, and ethically, whether my knowledge of these lists could be used to gain a competitive advantage over the field as a player myself.
I've spoken with other judges in my community, and in terms of publication of decklists, I'm told that the TO reserves that right. However, since many of our local players playtest in teams, I'm curious how much of my knowledge I am able to share with my team mates.
Perhaps there is no official answer regarding my concerns, but I feel like it's a huge ethical/moral question, and if nothing else, worthy of discussion.

Topic closed while an ‘O’fficial answer is prepared.

From the MTR: “Tournament Organizers are also allowed to publish this information once their tournament is complete.” (“this information” including deck lists)

There's nothing that prevents you, as a judge at the event, from accessing the decklists - with the TO's permission, of course. Once a deck is played in an event, it's public knowledge; it's also likely to change before the next event, or even from day to day. Deck tech is not the closely guarded secret it was in the 90s, before the Magic Dojo and other on-line tournament reports started to change that.

Don't feel like you're violating either policy or ethics, if you learn about the metagame from the deck lists at an event, and use that knowledge to your benefit. (And your friends or team mates? Well, good thing they know you, eh?)