Brands that haven't paid millions of dollars to the group behind the upcoming summer Olympics will need to watch their step on Twitter in the coming weeks.

The International Olympic Committee is threatening legal action against any non-sponsor brands that dare to tweet about the games or any of its associated trademarks, according to a letter obtained by ESPN.

Those trademarks include "Olympic," "Olympian" and "Go for the Gold," among a host of other related words and phrases.

Seemingly innocuous terms like "summer," "gold," "games," effort," "victory," "Rio" and "2016" are also off-limits if used in the context of the games, as are the various hashtags for the event — such as #Rio2016 or #TeamUSA" — any reference to Olympic results and all pictures taken at the Olympics, the letter says.

The U.S. Olympic Committee's chief marketing officer, Lisa Baird, sent the warning letter to the many companies that sponsor individual athletes but not the games or the U.S. team at large, ESPN says.

The blackout period, which excludes media companies, begins this Wednesday and lasts until three days after the Olympics have ended.

The crackdown is couched in the committee's controversial "Rule 40," which restricts how non-sponsors can advertise around the games.

The regulation has long been a headache for brands and athletes alike. Many Olympians have only a short window in which to cash in on their quadrennial spike in endorsement demand, and those who break the rule can face disqualification or have their medals stripped.

As the ban's start date drew near this week, a flood of Olympians and non-sponsor brands squeezed in final plugs for one another on Twitter. Some athletes accused the IOC of hypocrisy, comparing the hardline rule to the committee's supposedly lenient treatment of doping scandals.

if your sponsor says good luck to you in Olympic time you face being booted out #rio2016,but drugs cheats??! #rule40 https://t.co/WUhOTuaAk9 — Kelly Sotherton (@KellySotherton) July 26, 2016

All #Rio2016 athletes plugging their sponsors to death today #Rule40 — Kelly Massey (@kellymassey400) July 26, 2016

First rule of the Olympics: you don't talk about the Olympics. #Rule40 — Brent Lakatos (@BrentLak) July 27, 2016

International Olympic Committee:

Systematic Doping ✅

Sponsors supporting their athletes🚫

🤔🤔 #Rule40 #Confused — Chad Noelle (@ChadNoelle) July 27, 2016

#Rule40 starts tomorrow so I won't be able to say Thank You to my sponsor. THANK YOU FOR EVERYTHING @newbalance 🇺🇸 pic.twitter.com/udSEIPhsIA — emma coburn (@emmajcoburn) July 26, 2016

An anonymous party even took out a billboard campaign at the U.S. track and field Olympic trials in Oregon this month that poked fun at the restrictions.

“Good luck, you know who you are, on making it you know where,” one of the intentionally vague advertisements read.

Rule 40 is ostensibly in place to prevent the "over-commercialization" of the Olympics and cut down on unneeded distractions from its core mission — world-class athletic performance and friendly competition between countries. That may be true, but in practice, it also drives up the going rates of sponsorships and thus allows the committee to reap a bigger windfall.

Official Olympic sponsors, which include big multinational conglomerates like McDonald's, Coca-Cola and Procter & Gamble, pay upwards of an estimated $100 million for the privilege, while U.S.-only sponsorships go for a reported $40 million. Next month's games in Rio de Janeiro will reportedly be the most lucrative Olympics ever.

Thanks to years of lobbying from athletes, Rule 40 was loosened last summer so that brands that aren't official sponsors could apply to run tightly controlled campaigns featuring Olympians in the months leading up to the games.

The catch: They still aren't allowed to include any of the above-mentioned Olympics-related intellectual property in the ads.

Image: mashable

Image: mashable

GoPro, Pepsi-owned Gatorade, General Mills and Under Armour were some of the many brands that took advantage of the rule change, showcasing various Olympians while impressively dodging the committee's extensive list of forbidden words.

Opprobrium over the rule is nothing new, and it's not unique to the IOC. The NFL, for instance, also closely guards usage of Super Bowl-related words and phrases every season, which is why so many advertisements refer only to the "Big Game."

"It’s a situation that arises every two years when non-sponsors seek to leverage the golden glow of the Olympic Movement," said Shawn McBride, executive vice president of sports at marketing agency Ketchum Sports & Entertainment, in an email.

"The IOC – and USOC – are [now] attempting to balance the need to protect their [intellectual property] and their sponsors’ investment against providing opportunities for athletes to receive support and earn income from brands outside the official partner family," he added.

But there's a big difference between the business opportunities for American football players, who are generally sought after on Madison Avenue all year long, and Olympic athletes, many of whom play sports that might only catch the public's attention once every four years.

The NFL and other major sports leagues also function more like trade groups for their respective member teams, which are most often for-profit corporations, whereas the IOC is a not-for-profit bureaucratic body that's often mired in corruption charges.

The inclusion of social media under the blanket ban also adds an interesting twist. Under the rules laid out in the letter, an act as minor as a brand retweeting a post from the IOC's account could be considered an offense.

Whether or not this rule — which seems to strain the definitions of intellectual property law — will prove enforceable remains to be seen. But risk-adverse brands will likely avoid testing the committee all the same.

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