Well, Acclaim had the publishing rights, but didn't own TCoS. TCoS itself was made by Spellborn N.V., which used a company named Spellborn Works B.V. to actually develop the game.
Spellborn N.V. holds all the I.P. and assets. Spellborn Works created the game (together with Khaeon), and Spellborn Works went bankrupt.
Spellborn N.V. itself still exists, and is still the I.P.-holder. We can't use that American law, because the IP is in hands of a Dutch company.

Acclaim was nothing more than a publisher, who published what Spellborn N.V. provided to them, but they only had the rights to run the game, not the rights to the game itself.
MMORPG licensing is kind of messy...