This summer’s traumatic shootings of innocent black men and police officers across the United States has prompted many professional athletes use their platforms for social activism. During their season, WNBA teams and players have led by wearing pregame protest shirts and speaking at press conferences ― but it’s now costing them thousands of dollars.

On Wednesday, the WNBA fined the New York Liberty, Phoenix Mercury and Indiana Fever for wearing black shirts during warm-ups in solidarity with the Black Lives Matter movement. Each team was fined $5,000 and its players were fined $500, according to the Associated Press.

“We are proud of WNBA players’ engagement and passionate advocacy for non-violent solutions to difficult social issues but expect them to comply with the league’s uniform guidelines,” WNBA President Lisa Borders said in a statement provided to the AP.

David Sherman via Getty Images Lindsay Whalen #13, Maya Moore #23, Rebekkah Brunson #32, and Seimone Augustus #33 of the Minnesota Lynx attend a press conference to speak about recent shootings and racial profiling.

However, the WNBA’s apparent pride in its players’ activism and media attention is up against a stiff and unsettling adherence to the rule book. The Liberty have worn the plain black shirts four times total and did it again on Wednesday against the Washington Mystics on the road. Mercury and Fever players wore them Tuesday night. WNBA rules state that uniforms cannot be altered in any way.

It didn’t matter that the shirts were made by Adidas, the league’s official uniform supplier. It also didn’t matter that wearing plain black warmups — as opposed to shirts with text — began as a compromise between the Liberty and its players, who wanted to build off the momentum sparked by the Minnesota Lynx’s protest shirts and a press conference given earlier this month. Aware of the uniform rules, players informed the league office last week of their protest plans. In a laissez-faire manner, the WNBA decided to not prohibit the shirts for that week’s games.

At the beginning of this week, however, the league sent out a memo reminding teams of its uniform policy, noting that it would be enforced moving forward. Following NBA Commissioner Adam Silver’s stated preference for players to use social media, pregame and postgame press conferences and community events for political and social activism as opposed to the court, the WNBA encouraged players to use those platforms for expression instead. Their warning went unheeded.

The WNBA’s decision to take action against its players has already drawn sour reactions from around the league. Last night, Mercury forward Mistie Bass vented her frustration with, in her mind, the league’s double standard.

Don't say we have a voice and then fine us because we use it. #notpuppets #cutthestrings — Mistie Bass (@A_Phoenix_Born) July 21, 2016

The league’s fine is surprising given that dozens of players wore the black warmups with approval from their teams ― and considering that other professional leagues have not issued fines after player protests.

In December 2014, many NBA players, lead by superstars LeBron James and Kobe Bryant, wore black “I Can’t Breathe” warmup T-shirts in protest over grand jury decisions not to indict police officers who killed Eric Garner and Michael Brown. NFL players have also made “hands up, don’t shoot” gestures during games.

But the NBA and the NFL ― yes, the same NFL that fined players last season for dedicating a small uniform accessory to a dead parent ― decided against punishing its players. Fining LeBron James or any other major star for social activism is a bad public relations move.

There’s a coldness to the WNBA’s punishment that seems to go against its progressive values. Instead of making an exception for its passionate, mostly black players during a historically troubling period of social and racial unrest in the U.S., the league is prioritizing ticky-tack by-the-book rules.

More voices need to be encouraged, not fined ― and silenced.

CORRECTION: The players were fined $500, not $5,000 as previously stated.