"Public domain" refers to works that have no copyright protection, generally due to their age. I don't think there's much an argument that this comic is in the public domain.
There are, however, strong arguments supporting the public's the right to access, copy, and redistribute the comic.
Roughly the same question came up in White v. W. Publ'g Corp., 29 F. Supp. 3d 396 (S.D.N.Y. 2014), where lawyers brought copyright actions after finding their briefs publicly available on Westlaw and LexisNexis. The court granted summary judgment for West and Lexis after finding that incorporating their briefs into their online databases was fair use. The court ran through the standard fair-use factors and concluded that none of them favored the plaintiffs:
- The work was transformative because the lawyers wrote the briefs to secure specific legal outcomes for clients, while West and Lexis used them as parts of an interactive research tool.
- The nature of the copyrighted briefs was to offer "functional presentations of fact and law," making them factual works with less copyright protection that more creative works of fiction.
- West and Lexis copied the entirety of the copyrighted works, but doing so was necessary to integrate the documents into the databases.
- The use of the briefs did not impair the market for the originals because there was no meaningful market for licensing the briefs.
As always, the fair-use analysis is fact-intensive, and there are important differences between the two cases, but I'd be comfortable arguing for a broad application of fair-use to most copies of the comic. Even the most egregious case, -- imagine you just pulled it down from PACER, printed off 100 copies, and sold them as "tales of corporate intrigue" for $5 each, you're still in largely the same position as Lexis:
- Your work is transformative because the lawyers made it to secure a specific legal outcome, while you are using it as a device for entertainment. This points toward fair use.
- The nature of the copyrighted work remains a functional presentation of fact and law, i.e. a factual work with reduced protection. This points toward fair use.
- You would be copying the entirety of the copyrighted work -- or maybe less, if you omitted the several pages leading into it -- but doing so would be necessary to tell the whole story. This is largely neutral.
- The effect on the market is your biggest vulnerability, because there is perhaps some conceivable market for licensing a legal filing when it is as creative as this. But I think it probably remains small and is unlikely to .
But in the end, you have at least two fair-use factors cutting in your favor, and maybe even three or four. And even if it's not fair use, this might be a rare case where there's a difference between fair-use protection and First Amendment protection, as the First Amendment protects both your right to access court records, Press-Enterprise Co. v. Superior Court, 478 U.S. 1, 9 (1986) (“If the particular proceeding in question passes these tests of experience and logic, a qualified First Amendment right of public access attaches.”), and your right to distribute information you've legally obtained, Bartnicki v. Vopper, 532 U.S. 514,(2001).