Strategems - Reroll any single dice

"You can reroll any single dice"

Can I use this to reroll a dice my opponent has rolled?

Lol. I assume not, but on the other hand, I don't see anywhere it says you can't

Nowhere in the rulebook does it say, HOWEVER my interpretation goes:

Its a REroll. A REroll by definition is a repeated roll.
If you did not roll the die originally, it would not be a REroll, it would just be a roll.
The rule says YOU may REroll. Meaning YOU would REPEAT a roll you have already made.

Granted, this is a ridiculous convoluted way of reading it, but it works for me.

I'd tend to agree but in the drive to simplify I think we're still going to end up with dozens of loopholes you could drive a Land Raider through.