I recently went to a tournament and the TO made a ruling that I don't really agree with. I'm curious what you guys think.

He rules that while player 2 is overlapping an asteroid or debris field it doesn't obstruct his attacks, because asteroid and debris fields have no effect. I argued that the effects for obstacles are clearly defined in the rules and that obstruction isn't technically an "effect". What do you guys think?

I agree with you, this is erroneous ruling, because DT language (When one of the second player's ships overlaps an asteroid field or debris field, that obstacle has no effect) uses "when" clause and not a "while" clause. Therefore, this condition is triggered only once when the ship actually lands on asteroid and is not in effect later during shooting.

Well, if the TO wanted to rule that it didn't obstruct his attacks, it should have applied to your attacks as well. The DT wording is that the obstacle "has no effect," it does not specify that it has no effect for that player. So by that TOs interpretation, while the second player overlaps an obstacle, it has no effect on the game.

I mean, the ruling was wrong anyway. PT gives the reason why. But if they were going to argue for that resolution, they should have followed it all the way to its conclusion.

Exactly.

Line of Sight is completely separate to the Overlap rules. There is no advice on how to deal with line of sight while overlapping, because the overlap is irrelevant to it.

You ignore the overlap... Well done. Too bad your line of sight is still blocked by a whole other section of the rulebook