In a reaction that went viral on Twitter, Trump called the 69-year-old Robart a "so-called judge" whose "ridiculous" opinion "essentially takes law-enforcement away from our country."
To those who know Robart, who has been on the federal bench in Seattle for more than a decade after his appointment by another Republican, President George W. Bush, the ensuing drama surrounding the move was a far cry from the judge's standard.
"He is relatively apolitical," said Douglas Adkins, a private equity investor and former investment banker who has known Robart since childhood. "He's not a conservative or a liberal. He's a man interested in the law and fairness."
Late on Friday, Robart grabbed national headlines with his decision to temporarily lift Trump's week-old travel ban for citizens of seven mainly Muslim countries and refugees. His ruling was just a first step in considering the merits of the case challenging the ban. The Justice Department on Saturday filed a formal notice that it intends to appeal the ruling.
As a candidate, Trump had criticized federal judge Gonzalo Curiel, who was overseeing a case against his Trump University - arguing Curiel could not be impartial because of his Mexican heritage and Trump's vow to crack down on Mexican immigrants.
But by lashing out at Robart as president, Trump's anti-judiciary stance takes on new importance: it hits at the very heart of the checks and balances system meant to protect the country from government abuse of power.
Coincidentally, in his wide-reaching ruling on Friday, Robart emphasized that the three branches of government - the executive branch, Congress and the judiciary - should function as equals.
"The work of the Judiciary, and this court, is limited to ensuring that the actions taken by the other two branches comport with our country's laws, and more importantly, our constitution," Robart wrote.
Reached by email, Robart declined to comment on Trump's tweets.
A graduate of Whitman College in Walla Walla, Washington, and Georgetown University Law Center, Robart spent 30 years in private practice at the law firm now known as Lane Powell, before being appointed to the bench by Bush in 2004.
Adkins said Robart and his wife have no children but have been foster parents to several immigrant children over the years, primarily from Southeast Asia. Robart could not be reached for comment.
The judge served in the past as the president of the Seattle Children's Home and was a former trustee of the Children's Home Society of Washington, according to his official biography on the federal court website. Those organizations provide mental health services for at-risk youth and help troubled families.
"His involvement with children may have helped contribute to his understanding of the people impacted by this ruling but would not have shaped his interpretation of the rule of law," said Paul Lawrence, who was one of the attorneys who filed an amicus brief backing Washington State in the immigration case.
'PREVENTABLE HUMAN SUFFERING'
During his confirmation hearing, Robart recalled providing pro-bono legal services early in his career to "people who in many times felt that the legal system was stacked against them." He said he learned that the law "could be, if properly used, an opportunity for them to seek redress if they had been wronged," according to a transcript of the testimony.
Often sporting bow-ties with his black robes, Robart is known for saying from the bench in 2016 that "black lives matter." He cited the statement popularized by protesters during a hearing about a 2012 consent decree with the federal government that required the Seattle police department to address allegations of bias and excessive force.
In 2011, Robart put a temporary hold on a state rule change that would have cut government funding for disabled children and families in Washington.
"When faced with a conflict between the financial and budgetary concerns ... and the preventable human suffering," Robart wrote in that opinion, "the balance of hardships tips in the favor of preventing human suffering."
Adkins said he thought his friend would be able to take Trump's attacks in stride.
"His view is that criticism is important," said Adkins.
Banner and thumbnail credit: Reuters, Carlos Barria