Meredith, we don't have that problem in New York. I think you could take all the Codium you like. No one would even know what it was. I could fill a fifty gallon drum with the stuff in a half hour.
I once had a Sea Urchin collecting business here in NY and I called the Dept of Envirnmental Conservation to see if I needed a permit to dive for urchins like I have for lobsters. No one there even knew what an urchin was. So I never got a permit and never needed one. I am sure no one there knows what Codium, Ulva, hermit crabs, or just about anything else is either unless it is a commercial food item.
I don't think anything here is protected unless it is endangered or used for food.
Paul