Since now.
When we set out to update the ferrous dragons, we tried to remain as true to the original source material as possible. Changing the alignments to all lawful was probably the biggest retcon we made. We did this for two reasons: First, it helped give them a more identifiable niche in the true dragon milieu. Chromatics are evil; metallics are good; gems are neutral. Since the bulk of the ferrous dragons were already lawful, and their society seemed so obviously lawful, we decided to take the plunge and retcon the others into an all-lawful alignment. The second reason was to pave the way for another group of dragons that are all chaotic. I don't have a copy of the issue yet, so I'm not sure if the reference remained, but in the original submission we mentioned this chaotic group by name.
I hope the retcon isn't too jarring. We made it with the best of intentions.