From the TA FAQs:
Why can’t reserves pick up flying on Red Flag Days?
As long as it’s not a day off you can. Allowing a reserve to pick up flying on a day off could possibly interfere with FAR 117 legality.

Currently, both on reserve or as a line holder I can pick up flying on my days off. How does this answer make sense? I can't even find it in the new contract.

On a related note, what chaps me is that whole belief that reserves shouldn't be able to pick up needed flying on days off. We get emails from CPO asking us to pick up premium trips but we can't pick them up if we are on reserve because of the potential of running into 117 issues.. When I've been a line holder I am closer to busting 117 rules than when I've been on reserve if I were to pick up trips on days off.