Sprigman points out that the copyright for the 10th edition of the Bluebook (now in its 19th edition) has expired. He goes on to argue that much of the 19th edition is indistinguishable, and that courts' requiring lawyers to use Bluebook citations transforms the Bluebook's rules from copyrightable material into "government edicts."
From the later paragraphs of the letter:
I'm no expert in copyright law, so I'm not sure how far Sprigman's arguments will go. But I can't help but hope that Sprigman's Baby Blue project will succeed. Until then, however, I will get by with my hard copy of the Bluebook (and the publicly-available California Style Manual).
Based on what we’ve learned, we have embarked on a joint project with Public Resource to create and publish a public domain version of The Bluebook – a project we refer to as Baby Blue. Our project will mix public domain portions of the 19th edition with newly-created material that implements the Bluebook’s system of citation in a fully usable form.
In short, The Bluebook will soon face a public domain competitor. And when Baby Blue comes to market, The Harvard Law Review Association is likely to face questions regarding why the public – including pro se and indigent litigants – are obliged to pay for access to a resource that is indispensable to all those who seek justice from our courts. The Harvard Law Review Association is likely also to face questions regarding the financial transparency of the current structure.