Hi there,
This came up during a game this evening, and I am unsure of the correct resolution. I had Admiral Vader, and had reduced the speed of one of my ships to zero, to save it blundering into a Neb execution line, thinking that at speed zero I cannot spend a def token to resolve its effects during an attack, but that was all.
Then I had a thought, ....Doesn't Vader say you made spend a Def Token? me and my friend checked the rules and at the very end of the section detailing how you use Def Tokens when you are attacked, it explicitly states you cannot spend a Def Token if you are at speed zero. Obviously this was all written before Admiral Vader and his spend Def Tokens for Reroll shenanigans.
So the question is, can Vader spend a token for a reroll if the ship is at speed zero, the rules say cannot spend at speed zero, but and it is a big but, it is in the section for spending tokens for defensive effects while under attack, and Vader is not spending the token to generate a defensive effect nor is the ship in question being attacked.
We decided during the game the "cannot" is preventing his ability, with the intent when I got home to post this here.