Dane Butswinkas, a prominent Washington, D.C., trial lawyer who led Perkins Coie’s successful court challenge to an executive order by President Donald Trump, has died at 65 while preparing for a trial in Arizona.

His family said the cause was a pulmonary embolism. Butswinkas was a partner at Williams & Connolly, where he spent 37 years and served a term as chair.

Known for handling high-profile civil and criminal cases, Butswinkas took on one of his most consequential assignments in 2025, when Perkins Coie hired him to lead its fight against a Trump executive order targeting the firm. The firm, now known as Ashurst Perkins Coie, challenged the order in court as other firms yielded to similar pressure.

A federal judge struck down the order as unconstitutional. The government has appealed that decision.

For Butswinkas, the case was a responsibility to be met directly, Williams & Connolly senior counsel Steve Raber told The Washington Post.

“Dane viewed this case as something he had an obligation to do without fear, without hesitation,” Raber said. “Some people, when the chips are down, start looking for excuses or start looking for the exit. That was not Dane.”

The challenge became a defining episode in a career that had already established Butswinkas as a leading litigator in the nation’s capital. At Williams & Connolly, he combined courtroom work with firm leadership over nearly four decades, earning the respect of colleagues as both an advocate and a mentor.

In a memorial announcement, Williams & Connolly chairman Joe Petrosinelli called Butswinkas an “extraordinary trial lawyer” who “worked tirelessly” for his clients. He also described him as a “devoted mentor and friend” to colleagues.

“He was a world class lawyer, partner and friend,” Petrosinelli said, “and left a legacy that will endure.”

Butswinkas’s death leaves colleagues and clients mourning a lawyer remembered for his commitment to the people he represented and for his willingness to take on a politically charged legal fight.