Not sure that is true. Why would there be laws requiring a company to throw someone out of its loyalty program? Most laws like that favor the consumer. For example, in most states in the US it is illegal for gift card balances to expire.
And to be honest, I wish Carnival had a rule like that, especially in regards to the folks who made Platinum under the old, easier-to-achieve rules. If you sail Carnival less than once every 3 years, are you really that "loyal"?