It does actually confirms in the terms of service that it's not allowed under section 3:

Square Enix shall be entitled to terminate any FFXIV Service Account (immediately and without notice) of any User who (1) was previously suspended or terminated by Square Enix and who Square Enix believes (in its sole discretion) re-registered using different registration information in order to circumvent or bypass such suspension or termination
Although as the above player, whether they choose to do anything is anyones guess, but technically they could.