I would suggest a trade (or send-for-postage) from the rusty gardens, but I am sure that would be upsetting to some (state Ag departments included), even if the giver was upright and honest about his garden/plant status, and the recipient didn't care (because they are already in the Rust Bucket or have cold winters).
It may be hard to predict how these state Ag departments would react to rust. I get the impression that they're mostly concerned with pests and diseases which could be a threat to commercial crops. Still, I would want to ensure that if they inspected the plant that there would be no traces of any pest or disease.
I would at least clip/strip any rusty foliage, and might give the plant a shot of fungicide a week beforehand, depending on the wishes of the recipient. A light Clorox dip wouldn't hurt either. You don't want to give an inspector any excuse to reject the shipment.
The first time I ever saw rust was at a Big Box store, maybe 8-10 years ago, on a new shipment of Stella Wanna-Be's which were still in the receiving area. I showed it to the manager of the garden department, and gave him a quick rundown on what it was. I also called the county Ag people, and was surprised to find that they really didn't care about daylily rust. To the store's credit, when I went back a few days later, all of the rusty daylilies were gone.