A new ban on clothing that might be considered "offensive" has frequent Carnival Cruise Lines travelers wondering who gets to decide what the word means.

Carnival's announcement last month of the new ban has triggered a debate over the difficulty of regulating speech in an era when society is more divided than ever, socially and politically, and discourse seems to have no bounds. It also raised questions about whether the ban is even enforceable and whether it infringes on free speech rights.

Carnival's brand ambassador and senior cruise director, John Heald, revealed the addition to Carnival's dress code on his popular Facebook page, saying it was added to the FAQ section of Carnival's website "in the past few days."

The new section reads: "All guests are expected to ensure their clothing and accessories are respectful to fellow guests. Specifically, items worn during the cruise should not contain any message that may be considered offensive or contain nudity, profanity, sexual innuendo/suggestions. In addition, clothing/accessories should not promote negative ethnic or racial commentary, or hatred or violence in any form."

Asked what prompted the change, Carnival spokesman Vance Gulliksen said it resulted "after some incidents were reported in the media about other travel sectors where customers were wearing clothing with very threatening messages."

The reports "started a discussion about how we were prepared to handle such a situation and the need for clarification to both guests and crew."

In October, CNBC posted a tweet from a United Airlines passenger offended by another passenger's T-shirt that suggested journalists should be lynched. Although the airline did not remove the passenger wearing the T-shirt, it later released a comment saying, "We condemn the statements made against journalists."

Among competing cruise lines, websites of Royal Caribbean and Norwegian include no policies regarding offensive or respectful messages or attire. Disney Cruise Line asks guests to avoid wearing T-shirts with offensive language and/or graphics to its adults-only onboard restaurants. During nights in which guests are encouraged to wear costumes, Disney asks them to choose ones that are "family friendly, not obstructive, objectionable, offensive or violent."

Heald, who engages with Carnival fans daily on his Facebook page, said he brought up Carnival's new policy in response to a post about a woman who threatened to wear "disgusting and lurid shirts" on her cruise.

Quoting the fan who alerted him to the woman's threat, Heald posted: " 'She also says she is never sailing Carnival again and is going to advertise another cruise line with a slogan farewell [expletive] ... My question is will someone on the ship stop her from doing this?' "

Heald responded that Carnival won't allow the woman to follow through on her threat. "I hope this lady changes her mind and despite whatever she may think of me will have a brilliant cruise and enjoy the service and the fun that the crew will give her."

In an example of Heald's social media reach, 23,500 followers responded to a poll he posted asking whether they agree with the policy.

A decisive majority — 93% — of respondents said they agreed.

While Heald assured his followers that the policy would be enforced "strongly," an editorial on the cruise-oriented website cruiseradio.net predicted that Carnival wouldn't follow through.

Carnival spokesman Gulliksen said that while Carnival crew members are "not onboard to be the clothing or expression police," staff members will nonetheless "look out for guests wearing clothes with inappropriate images or language and ask them to change as needed."

He added, "We will evaluate situations on a case-by-case basis and take appropriate steps as necessary."