The lawyer who filed the motion to seize the ship is from Mississippi and claims they did it to 'get Carnival's attention', so I doubt it will be a common thing happening. He likely found some little part of the maritime law which allowed it and ran with it, and the magistrate was backed into a corner. Another report
For those with a Google account, you can read the lawsuit here . It appears that they based the seizure on the fact that Carnival plc and Utopia are not registered corporations in Texas. If they were, the seizure would not have been approved.