A question came up in a game where my opponent was flying Han Solo. Han's ability states that all dice that can be re-rolled must be re-rolled. Does changing an eyeball to a hit exclude it from being re-rolled? My instinct was that it doesn't because changing a result is different than modifying it, but he disagreed and said that he could spend a focus to "lock in" those results and then re-roll any remaining blanks using Han's ability.

The only thing that prevents a die from being re-rolled is if it was already re-rolled (From Rules Reference pg. 13: Dice can be modified by multiple effects, but a die cannot be re-rolled more than once.)

So, that modified dice must be re-rolled since it was not already re-rolled.

IF Han's opponent first used a Sensor Jammer to turn a [boom] into an [eye] then that die would have become ineligible for a reroll because the Sensor Jammer specifically says so. Spending the Focus to turn that [eye] back into a [boom] can be done but a reroll is prevented by the Jammer and not the token.

A given die my have any number of modifications done to it except that it can only be re-rolled one time. Modifications can happen before and after.

Or being even more explicit...

• The Combat Phase has 7 ordered steps
  1. Declare Target
  2. Roll Attack Dice
  3. Modify Attack Dice
  4. Roll Defense Dice
  5. Modify Defense Dice
  6. Compare Results
  7. Deal Damage

Modifications are only made during the two relevant steps (in bold), and only apply to the dice just rolled.

• During the "Modify Attack Dice" step, the defender modifies first, then the attacker.
• During the "Modify Defense Dice" step. the attacker modifies first, then the defender

If a dice modification would re-roll the die, The die cannot be re-rolled again. So if the defender or attacker had already re-rolled the die, than Han's ability could not re-roll that die.

Also, card rules (e.g. Palaptine) often say something like "The die result cannot be modified again." When this happens, that die is locked in. So if Palpatine could be installed on the Falcon (insanity...), a player could "lock-in" the die preventing it from being re-rolled by Han's ability.

But as stated by others, in the case described, Focusing before Han does not re-roll any dice, and Han's ability would be a full re-roll. He should use the focus after Han's ability

The best example is if Han has a Target Lock and a Focus token.

He could roll his 4 dice for a range 1 attack, getting blank blank eye hit. He could then reroll the blanks by spending his target lock getting say, hit crit. If he did, he would then be able to spend his pilot ability to reroll dice, but couldn't reroll the ones he rerolled with the TL. He must then reroll the eye hit only, getting say, eye eye. Now all the dice have been rerolled, so none can be rolled any more. But he could then spend his focus to turn the eyes into hits, because that's not rerolling.

The best example is if Han has a Target Lock and a Focus token.

He could roll his 4 dice for a range 1 attack, getting blank blank eye hit. He could then reroll the blanks by spending his target lock getting say, hit crit. If he did, he would then be able to spend his pilot ability to reroll dice, but couldn't reroll the ones he rerolled with the TL. He must then reroll the eye hit only, getting say, eye eye. Now all the dice have been rerolled, so none can be rolled any more. But he could then spend his focus to turn the eyes into hits, because that's not rerolling.

For anyone reading this example and scratching their heads wondering why Han would choose to use his pilot ability to reroll the one eye in his [boom][boom][kaboom][eye] rather than just spending his focus token to flip it to a hit: he probably wouldn't*. This example is constructed to show the interaction between two different sources of rerolling, and isn't likely to be seen in the wild.

*: The only situation where I could see choosing to reroll an eye rather than spend a focus is when you're attacking a high hull target and you know your maximum number of hits isn't going to kill it. I actually lost a TIE Shuttle the other day to a lucky Direct Hit after my opponent chose to use his Target Lock to reroll an eye and got a crit through.