OK, a few things to point out here.
This ruling is
not about copyright holders clawing back works that properly and legitimately entered PD.
The ruling asserts that certain foreign works were
improperly classified as PD, due to the foreign nation failing to follow its agreements to respect the originating nation's copyright laws per the Berne Convention or other mitigating circumstances (e.g. errors in paperwork). §514 of the Uruguay Round Agreements Act moves to restore those copyrights and sets up specific limits on protections for those who inadvertently used the works while they were misclassified as PD.
That's why the ruling explicitly states: "Section 514 does not restore copyrights in foreign works that entered the public domain through the expiration of the term of protection." (p 6) It's only when the nation failed to properly enforce copyright protection in harmony with the agreements it signed that protection resumes.
The Techdirt article is horrendously biased; it's short on legal reasoning and long on hysteria and knee-jerk reactions. For a more even-handed summary:
http://blogs.forbes.com/docket/2010/...from-the-dead/