I am looking at guys like scum Boba and Ibtisam, both of their cards allow for dice rerolls. I was talking to someone about how this works and a question came up... are these dice rerolls once per dice modification stage, or once per round?

for reference, here are the card texts:

"When attacking or defending, you may reroll 1 of your dice for each enemy ship at Range 1."

"When attacking or defending, if you have at least one stress token, you may reroll 1 of your dice."

I was guessing that these abilities were once per dice modification stage, but a guy I know pointed out that since it doesn't specify that (and that it specifically calls out dice numbers) it should be once per round, but I do not think that it works like that...?

Related scum Boba question. Does his ability split between his attack and defense dice? Like, two enemies are at range 1, is he allowed to reroll 2 attack dice and two defence dice, or does he split it so he can only reroll 2 dice total? Like reroll 1 attack and 1 defense, as long as it adds up to the amount of enemies at range 1?

Once per modification stage.

If it's once per round, it will say so.

Boba gets full use on Offense AND on Defense.
When surrounded by 2 enemy ships at Range 1, he can reroll up to 2 dice on attack, and he can reroll up to 2 dice on defense.

In both cases, you get the reroll(s) every time you attack or defend, at the dice modification step. The same applies to upgrades like Lone Wolf. If any of these effects were once per round, it would specify that, like on the Emperor Palpatine crew card.

For the second question, Boba doesn't have to split his rerolls. He gets the full amount of rerolls for each attack roll and each defense roll.

Edit: In other words, what Dracon said.

Ah thank you, that is what I figured but it is good to be sure about this stuff

Ah thank you, that is what I figured but it is good to be sure about this stuff

Just to pile on, the right terminology is those abilities (and, by default, most things in X-wing) activate once per opportunity. In this case, the opportunity is "when attacking or defending"--so you can activate Fett's ability once for each attack roll he makes, and once for each defense roll.

Ah thank you, that is what I figured but it is good to be sure about this stuff

And for future reference, FFG are pretty good at defining any ability that only gets to be used 'once per round'. If it lacks that phrase, you can generally assume 'once per opportunity' to be more likely.