I did have a problem buying Jacob hoggs ( purchased as unregistered) that had pedigree tags in but weren't pedigree animals, when I phoned the society to check if they were eligible for registration, they were annoyed that the owner had tagged unregistered animals with JSS tags.
As it turned out they had changed hands 3 times previously to me buying them, as inlamb hoggs, and had no IED tags in at all.
I'd follow the law first, then the society, as they do check at pedigree sales that the animals. The above mentioned Jacobs were bought privately at least if I'd have bought them at an Auction any tagging issues would have been highlighted before it became my problem.
Like Tim W says put the tags in the freezer and they will harder up and not bend, as I find my Ritchey tags can be awful sometimes! Good Luck