When athletes march in the Olympic opening ceremonies Friday night in Rio de Janeiro, some of them will be donning the national uniforms of countries they’re not actually from.

For an event that represents so much  national pride, where victories or defeats live in lore for decades, many athletes will represent another country, either because of heritage or because it may be the only way they could compete in the games.

But is switching nationalities just to compete in the games in the Olympic spirit?

Take pole vaulter Giovanni Lanaro. He was born, raised, educated, and trained in southern California, but in Rio he’ll be competing for Mexico. While he is an American, his mother was born in Mexico, and the Mexican national team only requires that you have Mexican heritage in order to compete for them.

“What's wrong with being proud about competing for Mexico?” he told the Los Angeles Times. “I don't see anything wrong with it.”

Lanaro isn’t the only American competing for Mexico in the Olympics. He joins a women’s basketball player, a wrestler, and five boxers.

The Olympics are where the world’s best athletes compete. Some teams, like the U.S., are full to the brim with top talent. Some of the best American athletes are inevitably left off the Team USA roster, even if they can compete on the world stage.

Lanaro is competing for another country because of his pride in his heritage. But he is also competing for a national team that could use his talent. The same can be said for runners David Torrence for Peru, Alexi Pappas for Greece, and Peter Callahan for Belgium, who are all Americans with ancestors born abroad. As Torrence put it to Runner’s World:

It boils down to why do I run? I love competing and racing and everything involved in that process, but I also really love to work with kids, inspire youth, and I think I am a part of a movement to get people running. In the U.S., there’s going to be a full team of people in every event in almost every sport. There’s no shortage of heroes or role models out there. But in Peru, they’re not sending full teams, they’re not sending a ton of athletes, not only in track and field, but across all sports.

And if an athlete has the talent, why be left out of the Olympics? Peter Spiro of Slate argued before the 2014 Winter Olympics:

It makes more sense to allow free Olympic association, with athletes playing for any team that will have them. The Olympic Charter notes that “the Olympics are competitions between athletes in individual or team events and not between countries.” That’s exactly right. We don’t require our major-league ballplayers to hail from the cities they play for, so why should we demand anything different of our Olympic athletes?

Follow the story lines of past Olympics and you find they aren’t just about countries, like the U.S. hockey victory over the Soviet Union in 1980, but also about people, like Michael Phelps’s record 22 medals.

Callahan, the Belgian olympian, takes an almost socialistic attitude toward the Olympics, saying athletes should “rightfully be distributed around the world and make those championships even better, even more competitive, even more exciting.”

The Olympic Charter requires only that an athlete be a national of the country for which he or she is competing. If they want to compete for a different nation, it has to be three years after they last competed for their country of origin. Becoming a national is not difficult for a talented athlete.

But there is a dark side to trying to distribute talented athletes to other countries. As Foreign Policy wrote in 2014, “opportunism knows no borders.” They write:

Qatar, meanwhile, invests heavily in athletes from both Kenya and Bulgaria. In 2000, Qatar’s government bought an entire Bulgarian weightlifting team — eight athletes in total — in exchange for citizenship and a little over $1 million. In 2003, it also reportedly bought two Kenyan long-distance runners: Stephen Cherono and Albert Chepkurui, who duly became Qatari Olympians Saif Saeed Shaheen and Ahmad Hassan Abdullah (neither Cherono nor Chepkurui were actually Muslim).

Azerbaijan, for its part, has heavily recruited foreign-born athletes; half of its 50-person national team in the 2012 Olympics were naturalized citizens. Great Britain’s Olympic team in 2012 had 60 foreign-born athletes, who were labeled “Plastic Brits” by The Telegraph.

The U.S. even takes place in the practice. During the 2008 games, the U.S. hurried citizenship status for a Polish kayaker, a Chinese table-tennis player, a triathlete from New Zealand, a Kenyan distance runner, and an Australian equestrian, among many others who qualify for EB-1 visas for people of “extraordinary” abilities. Importing athletes has worked for the U.S., producing eight medals between 1992 and 2004, according to The New York Times.

While competing for a different country can raise an athlete’s international profile, it could lead to criticism, as well. When South Dakota native and WNBA star Becky Hammon decided to play basketball for Russia during the 2008 Olympics, The Houston Chronicle asked, “Is Hammon a traitor?”

U.S. women’s coach Anne Donovan even said, “If you play in this country, live in this country, and you grow up in the heartland and you put on a Russian uniform, you are not a patriotic person in my mind.” (The U.S. would beat Russia in the semifinals and eventually won gold. Russia won bronze.)

Jacques Rogge, the former International Olympic Committee president, had his own reservations about athletes changing nationalities. He said in 2012, “We cannot oppose it because it’s a sovereignty matter, but let me tell you very frankly: I don’t love that.”

In the first modern Olympic games in 1896 in Athens, athletes by and large were not grouped by nations. Hungarian athletes were the only ones who competed under a national banner. It was a competition among 280 athletes in 43 events. It was not a competition among nations, even if they came from 14 different nations.

In this Olympic games, 11,000 athletes will compete in 306 events under the banner of 206 nations. In the eyes of the athletes competing under the flag of a country that’s not home, they’re competing in the Olympic spirit as much as anyone else.