Several of Carnival Corp.'s cruise lines adopted new policies that prohibit online travel agencies or cruise sellers from bidding on the lines' trademarked search-engine keywords.

The similar policies, adopted by Carnival Cruise Lines, Cunard Line, Holland America Line, Princess Cruises and Seabourn Cruises, went into effect Jan. 1.

A notice posted on Carnival's travel agency Web site, bookccl.com, said the prohibited keywords include names of its ships; its marketing slogans (World's Most Popular Cruise Line, for example); its products (Total Choice Dining, e.g.), or any other trademarked term.

Agencies also many not bid on keywords formed by inserting typos into trademarked terms. If an agency buys generic cruise-related keywords or keywords for destinations or ports served by Carnival on broad match keyword terms programs, Carnival said, the bidding agency "must ensure that its ads do not appear for consumer searches which include Carnival's Property or Typos in combination with the generic keywords."

If an agency fails to remedy a violation of the policy or if it commits a second violation, Carnival "reserves the right to temporarily suspend or permanently revoke (a) its authorization to book or sell cruise accommodations and/or (b) payment of commissions for cruise bookings that are made during the period of an uncured violation."

Carnival's policy also states that it reserves the right to take "appropriate legal action" against all parties who violate its intellectual property rights, the policy or its travel agency agreement.

Carnival did not provide a specific reason for the new policy. However, a higher number of bidders tends to drive up the cost of winning bids.

Carnival and its sister cruise lines are not the first travel suppliers to take action on the keyword issue. In 2007, American Airlines sued Google over the sale of the carrier's trademarks as keywords. A year later, the firms settled out of court. The terms of the settlement were not disclosed; however, ads no longer appear alongside results for searches of those trademarked terms. American's 2008 lawsuit against Yahoo is pending.

In 2004, InterContinental Hotels required third-party distributors to agree not to bid on or purchase placement rights for its trademarks. That policy led to a three-year rift with Expedia and Hotels.com. The following year, Marriott International also banned its online travel distributors from bidding on keywords containing Marriott trademarks.