They're fine. Completely totally fine. Make sure you're not giving them any of the bud part of the plant which has the psychoactive materials (seriously, why waste good bud on a chicken?), but just doing harmless, dried, sugar leaves and stems.
When my chickens *have* gotten in with budding plants, they actually don't like the buds, and will eat the plain leaves, skipping the flowers. (thankfully!!!) It doesn't seem to be a favorite plant for them, kind of like how they leave tomato leaves alone -- they much prefer broccoli leaves (chicken crack!!!).
I'm in Oregon, so totally legal here too. I'm breaking more laws with how many chickens I have, than what plants I'm growing!