A Yosemite National Park ranger was fired after hanging a pride flag from El Capitan while some visitors face potential prosecution for alleged violations of protest restrictions that have been tightened under President Donald Trump.

Shannon “SJ” Joslin, a ranger and biologist who studies bats, said they hung a 66-foot wide transgender pride flag on the famous climbing wall that looms over the California park's main thoroughfare for about two hours on May 20 before taking it down voluntarily.

A termination letter they received last week accused Joslin of “failing to demonstrate acceptable conduct" in their capacity as a biologist and cited the May incident.

"Really what a trans flag is, is a symbol of safety and a symbol acceptance,” Joslin, 35, told The Associated Press. “You're supposed to be safe in parks. What is happening now is that this message is saying that actually you're not safe in parks."

Joslin said their firing sends the message that if your identity isn’t compatible with the current administration, then you must be silent, or you will be eliminated.

Park officials on Tuesday said they were working with the U.S. Justice Department to pursue visitors and workers who violated restrictions on demonstrations at the park that had more than 4 million visitors last year, through both administrative action and possible criminal charges.

Joslin said a group of seven climbers including two other park rangers hung the flag.

The other rangers are on administrative leave pending an investigation, Joslin said.

Flags have long been displayed from El Capitan without consequences, said Joanna Citron Day, a former federal attorney who is now with the advocacy group Public Employees For Environmental Responsibility.

She said the group is representing Joslin, but there is no pending legal case.

On May 21, a day after the flag display, Acting Superintendent Ray McPadden signed a rule prohibiting people from hanging banners, flags or signs larger than 15 square feet in park areas designated as “wilderness” or “potential wilderness.”

That covers 94% of the park, according to Yosemite’s website.

Parks officials said the new restriction on demonstrations was needed to preserve Yosemite's wilderness and protect climbers.

It followed a widely publicized instance in February of demonstrators hanging an upside down American flag on El Capitan in the wake of the firing of National Park Service employees by the Trump administration.

Among the small group of climbers who helped hang the flag was Pattie Gonia, an environmentalist and drag queen who uses the performance art to raise awareness of conservation issues.

For the past five years, Gonia has helped throw a Pride event in Yosemite for park employees and their allies.

She said they hung the transgender flag on the granite monolith to drive home the point that being transgender is natural.

Trump has limited access to gender-affirming medical treatments, banned trans women from competing in women's sports, removed trans people from the military and changed the federal definition of sex to exclude the concept of gender identity.

Gonia called the firing unjust. Joslin said they hung the flag in their free time, as a private citizen.

Since Trump took office, the National Park Service has lost approximately 2,500 employees from a workforce that had about 10,000 people.

The Republican president is proposing a $900 million cut to the agency’s budget next year.