Opinion | Sports betting ads are out of control. For solutions, look overseas.

The online sports betting market exploded across the United States after the Supreme Court gave states the power to set their own regulations in 2018. The market is projected to earn $14.3 billion in revenue this year, with 11 percent of the adult population using online gambling apps, which offer casino games and the like in addition to sports betting. The European Union, with nearly 500 million people, is expected to see $11.7 billion in sports betting revenue this year; Britain, $4.5 billion, with 20 percent of its adult population gambling online. In Australia, the number might be $4.5 billion, with nearly 17 percent betting online; and in Canada — where 49 percent of adults bet online — revenue could be just under $1 billion for 2024.

As legal sports betting grows, so do its toxic side effects: gambling addiction, personal bankruptcy and mental health problems. High-profile scandals have raised concerns about preserving the integrity of matches — and the spirit of competition. It’s worth looking at how the United States’ peer countries, many with longer experience in dealing with legalized sports gambling, address these problems — starting with a key engine of betting growth: advertising.

Italy, Spain and the Netherlands have banned ads for sports betting during live games, known as “whistle to whistle” bans. This limits prop bets, or fast-paced, impulsive wagers on the results of individual athletic acts — kicks, throws or penalty shots — in the middle of a contest. The regulations differ across countries. Spain, for example, restricts gambling ads to the hours of 1 a.m. to 5 a.m. But Spain’s Supreme Court this year overturned some stricter ad bans. Italy bans betting ads across all platforms, including online, during live broadcasts.

Some countries restrict ads during hours and in places where they are more likely to be seen by children. Belgium limits gambling ads across all platforms during certain hours. Australia had plans to restrict when sports betting ads could appear, but the current government appears to have backtracked. In May, Bulgaria’s president signed a law prohibiting gambling ads on TV, radio, newspapers and websites. Ireland, Finland and Norway are also considering strict controls on sports ads. Britain has gone even further, since 2022 banning professional soccer players, celebrities and anyone known to have a large social media following among minors from appearing in gambling ads.

Canada’s Parliament allowed gambling in 2021; by 2022, more than 40 online betting outfits were established — accompanied by a tsunami of gambling ads. Some ads for BetMGM featured retired NHL Hall of Famer Wayne Gretzky and even current stars such as Connor McDavid of the Edmonton Oilers. The Campaign to Ban Ads for Gambling, led by Canadian Olympian Bruce Kidd, an emeritus professor at the University of Toronto, estimated more than 300,000 people were at risk of gambling-related harms, including “runaway debt, stress to families, low self-esteem, anxiety, depression, and even suicide.” Mr. Kidd’s group lobbied the Ontario parliament to restrict the use of athletes and celebrities in betting ads. But Mr. Kidd said the new rules had a major loophole; sports stars can still appear in ads, as long as they are promoting “responsible betting.”

Any attempt to regulate gambling ads in the United States might run afoul of America’s free-speech tradition. The same was true in Canada. But advocates of gambling advertisement restrictions in Canada cited the precedent of ad bans for cigarettes and cannabis. U.S. courts have generally ruled that the First Amendment protects commercial speech, while allowing for some health-related restrictions, such as requiring graphic images on cigarette packages. In 1986, the Supreme Court upheld Puerto Rico’s ban on casino advertising. Treating sports betting as a public health concern could allow more advertising regulation.

After the initial excitement over new revenue from gambling taxation, several U.S. states are having second thoughts and considering how to limit the collateral damage. Fortunately, other countries have run some experiments for them.