Smoking's allowed in our mob but I gave up a few years ago.
I got no objection if the FO wants the odd one, and if I don't
like it I just leave the cockpit for a few odd minutes when the
workload's low until he's had his fill.
Might work the same way if you ask the cappy nicely that if
he lights one up you would like to leave the cockpit till he's
done. Remember you'll be on THEIR turf buddy.