The country's five largest professional sports leagues want lawmakers in Pennsylvania, New Jersey and more than 30 other states to impose tough penalties on sports bettors who harass athletes. 

The NFL, NBA, MLB, NHL and MLS, along with their players associations, sent a letter to gambling regulators Tuesday urging states to pass laws that crack down on threatening behavior. 

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"Too often, individuals who lose sports bets direct threatening and harassing messages toward players, coaches, and their families via social media and in-person interactions," the letter said. "Threatening the safety of an athlete or their family members over a sports bet crosses a bright ethical and criminal line, and it is entirely unacceptable." 

The expansion of legal sports betting in the United States has come with increased public scrutiny of athletes in the college and professional ranks. One NCAA-commissioned study found a spike in online harassment of men's and women's basketball players during March Madness, and about one-third of players on Division I men's teams reported social media abuse. 

The Athletic reported in August that hostility from sports bettors has become a regular part of life for many baseball players. About 80 of the 100 players the Athletic surveyed said they had been confronted or contacted about a sports bettor either in person or online. 

"If your social media is private, they'll find your family members,"  an anonymous National League pitcher told the Athletic.

The coalition behind Tuesday's letter urged states to adopt a streamlined reporting system for leagues, teams, players and unions to document harassment. The coalition wants to see laws that give mandatory lifetime bans to violators who use state-regulated sportsbooks and mobile platforms. The letter also said commercial sports books should be compelled to monitor, flag and ban accounts linked to abusive behavior as a condition of maintaining their licenses.

"The safety and well-being of players, coaches, officials and their families must always come before a wager," the letter said.

Louisiana, Ohio, West Virginia and Wyoming have passed laws that align with the coalition's requests. Two of the nation's biggest sportsbooks, DraftKings and Fanatics, have begun using artificial intelligence to monitor social media abuse and identify people who harass athletes as part of a broader effort to root out unusual betting patterns and unlawful wagering by athletes. 

New Jersey lawmakers have considered legislation that would meet the coalition's requests, but so far have not passed a bill. Pennsylvania lawmakers have not put forth a bill to address the issue. 

In some cases, sportsbooks have taken action to punish bettors who target athletes. Track and field star Gabby Thomas was heckled in Philadelphia last year by a man whose bet hinged on Thomas losing a 100-meter-dash during an event at Franklin Field. The bettor later went on social media to claim he had "made Gabby lose," and FanDuel banned the man from its platform several days later.

Thomas addressed the situation in a social media post. 

"This grown man followed me around the track as I took pictures and signed autographs for fans (mostly children) shouting personal insults," Thomas wrote on X. "Anybody who enables him online is gross."

Former Minnesota Vikings running back Alexander Mattison also spoke out about receiving direct messages with racial slurs and calls for him to commit suicide after the Vikings lost to the Eagles in a "Monday Night Football" game at Lincoln Financial Field in 2022. Mattison said comments about his fantasy football performance were not uncommon, but the level of hatred in some messages after that game shocked him. 

"I hope the 60+ people who decided to come at me with disgustingly disrespectful messages tonight in DM's and comments, really reflect ... on what you say and how it could truly affect someone," Mattison said at the time. 

IC360, the technology partner DraftKings and Fanatics use to monitor betting integrity, told ESPN the company supports finding new strategies to deal with athletes being threatened and harassed by bettors. 

"True progress requires a unified response where leagues, operators, regulators and technology partners align around solutions to safeguard stakeholders across every touchpoint," IC360 co-founder and co-CEO Scott Sadin said.