Under tournament rules, can you use the range ruler in the movement phase? Also, if you can't, how would you know that a ship is within range 3 to put a target lock on and if they weren't, would you then lose the target lock in the attack phase?

And therefore your action would be wasted.

The rules as written for when exactly you are allowed to measure are currently broken (or at least able to be interpreted as such). I've submitted a a rules question to FFG for clarification.

In practice, you are allowed to measure whenever you have an ability that requires a measurement.

See "Competitive Rules" in the FAQ for a detailed explanation of how and when you measure for Target Locks.

The capsule version: in the case of a Target Lock, you are allowed to use the range ruler to measure the range to only the ship you're trying to lock. If it's in range, you must go through with the lock. If it's not, you can do something else, either attempt to lock a different ship or take a different action entirely.

In more general terms, any time you need to know whether a ship is at a particular range of another ship, e.g. when deciding if you can trigger Kanan (crew)'s ability, you are permitted (required, even) to use the range ruler to measure that range.

If you are choosing to target lock and then find out you can, then suddenly think that you wanted to focus instead, then really, you should have spent more time thinking before declaring your action.

If you have to choose another action due to failure to obtain a lock, the action you choose next should always have been your Second Priority action, not your first.

And don't say "Target lock Ship X" to check your/their weapon range in the activation phase.

If you want to see if you can TL a ship when there is another between you and the "intended" TL target you can measure even if the target ends up being (a LONG WAYS) out of range.

The other important thing to mention is that you don't resolve your actions (such as acquiring a target lock) in the combat phase - so you wouldn't be at risk of losing your declared action anyway due to the above responses in regards to being able to choose other actions if an available one you attempt is unsuccessful. Further, whenever you do perform an action, you are initiating a small pocket of extra steps that get inserted into whatever phase of the turn you're currently on. So for example any time a target lock action occurs, you handle the measuring and token assignment immediately and completely before proceeding with the rest of the game - there's no situation where you "save up" measuring steps for later.

So this came up in my playgroup a little bit ago, and I wanted to know what the general consensus was. Situation was that the player was very evidently within range 3 of a target lock (actually closer to range 1 to be more precise) to his defender, but declares an "attempt" to target lock and measures out with the range ruler. It seemed pretty apparent that he was measuring to see if it was within range 1 for other reasons than the target lock, but was manipulating the opportunity to serve other informational-gathering purposes. While I know the rules allows for this to happen, is there any penalty or judge call for a willful manipulation of rules?

This is not a wilful manipulation of the rules, it's actually entirely legitimate. Not only can you measure at that stage in the process, technically, you MUST measure when you attempt to acquire a Target Lock.

Reinforcing what thespaceinvader said, it's pretty common practice for players running PTL aces to declare a target lock with their first action to see if their maneuver needs to be augmented by a boost or barrel roll as their second action.

I've had situations where an opponent has declared a target lock, realized they were just within range 3 (and were forced to take the lock) and said something to the degree of "Oh, I didn't think I had that, I kind of wish I didn't"

Now what they can't do is take that opportunity to measure their arc. If you're seeing players measuring target locks from their arc lines, they're pushing a different kind of limit if you know what I'm sayin

is there any penalty or judge call for a willful manipulation of rules?

There is no penalty for any such thing. You may not like it, but unless the person is engaging in some sort of poor sportsmanship there's nothing a judge can or even should do about it.

As was pointed out, not only is what he did legal, it's technically required, and FFG has said they have no issue with people gaining inadvertent information when checking for a TL, information like the exact range or even the range to another ship.

It's worth noting that you can only measure to a single ship when you attempt a TL, unless they're not in range in which case you can try a different ship or a different action if applicable, and you must measure closest point to closest point, so you can't e.g. measure range in arc only (which might mean that you get a TL and the ship isn't actually in range to shoot, if you're arc-locked) and probably won't mean you get to check if it's in arc at all.

It usually would let you know if an attack was going to be obstructed, assuming the enemy ship was in arc or you wold be able to fire outside it.

It may seem odd, but it's a perfectly legitimate thing to do from a rules perspective to get measurements using the TL action, either of range to a ship, or of the fact that it's not currently in range. Just remember that it costs an action which would often be better spent on a focus or boost/br, and forces you to take a TL if you succeed - and that the action is not available to ships without the TL action, so TIE fighters, TIE interceptors etc can't get range checks this way.