Judge James Robart emerged from relative obscurity on Saturday as the first justice to come under fire from the president since he took office after his temporary order to lift Donald Trump's immigration ban.

In a reaction that went viral on Twitter, Mr Trump called the 69-year-old Judge Robart a “so-called judge” whose “ridiculous” opinion “essentially takes law-enforcement away from our country.”

To those who know Judge 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.

President Donald Trump lashes out at US judge on Twitter

“He is relatively apolitical,” said Douglas Adkins, a private equity investor and former investment banker who has known Judge Robart since childhood. “He's not a conservative or a liberal. He's a man interested in the law and fairness.”

Late on Friday, Judge Robart grabbed national headlines with his decision to temporarily lift Mr 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, Mr Trump had criticised 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 Mr Trump's vow to crack down on Mexican immigrants.

But by lashing out at Judge Robart as President, Mr 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, Judge Robart emphasised 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,” Judge Robart wrote.

Reached by email, Judge Robart declined to comment on Mr Trump's tweets.

A graduate of Whitman College in Walla Walla, Washington, and Georgetown University Law Centre, Judge 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.

Judge James Robart was appointed by George W Bush but is said to be "relatively apolitical"

Adkins said Judge Robart and his wife have no children but have been foster parents to several immigrant children over the years, primarily from Southeast Asia. Judge 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 organisations 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.

During his confirmation hearing, Judge 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.

Activists protest Donald Trump's proposed Muslim ban Show all 11 1 /11 Activists protest Donald Trump's proposed Muslim ban Activists protest Donald Trump's proposed Muslim ban People listen to speakers at a demonstration against racism and conservative presidential candidate Donald Trump's recent remarks concerning Muslims on December 10, 2015 in New York City. Dozens or demonstrators and activists converged at Columbus Circle to denounce the politics of Trump and the treatment of Muslim refugees both in America and Europe. Spencer Platt/Getty Activists protest Donald Trump's proposed Muslim ban People listen to speakers at a demonstration against racism and conservative presidential candidate Donald Trump's recent remarks concerning Muslims on December 10, 2015 in New York City. Dozens or demonstrators and activists converged at Columbus Circle to denounce the politics of Trump and the treatment of Muslim refugees both in America and Europe. Spencer Platt/Getty Activists protest Donald Trump's proposed Muslim ban People listen to speakers at a demonstration against racism and conservative presidential candidate Donald Trump's recent remarks concerning Muslims on December 10, 2015 in New York City. Dozens or demonstrators and activists converged at Columbus Circle to denounce the politics of Trump and the treatment of Muslim refugees both in America and Europe. Spencer Platt/Getty Activists protest Donald Trump's proposed Muslim ban People listen to speakers at a demonstration against racism and conservative presidential candidate Donald Trump's recent remarks concerning Muslims on December 10, 2015 in New York City. Dozens or demonstrators and activists converged at Columbus Circle to denounce the politics of Trump and the treatment of Muslim refugees both in America and Europe. Spencer Platt/Getty Activists protest Donald Trump's proposed Muslim ban People listen to speakers at a demonstration against racism and conservative presidential candidate Donald Trump's recent remarks concerning Muslims on December 10, 2015 in New York City. Dozens or demonstrators and activists converged at Columbus Circle to denounce the politics of Trump and the treatment of Muslim refugees both in America and Europe. Spencer Platt/Getty Activists protest Donald Trump's proposed Muslim ban People listen to speakers at a demonstration against racism and conservative presidential candidate Donald Trump's recent remarks concerning Muslims on December 10, 2015 in New York City. Dozens or demonstrators and activists converged at Columbus Circle to denounce the politics of Trump and the treatment of Muslim refugees both in America and Europe. Getty Activists protest Donald Trump's proposed Muslim ban People listen to speakers at a demonstration against racism and conservative presidential candidate Donald Trump's recent remarks concerning Muslims on December 10, 2015 in New York City. Dozens or demonstrators and activists converged at Columbus Circle to denounce the politics of Trump and the treatment of Muslim refugees both in America and Europe. Spencer Platt/Getty Activists protest Donald Trump's proposed Muslim ban People listen to speakers at a demonstration against racism and conservative presidential candidate Donald Trump's recent remarks concerning Muslims on December 10, 2015 in New York City. Dozens or demonstrators and activists converged at Columbus Circle to denounce the politics of Trump and the treatment of Muslim refugees both in America and Europe. Spencer Platt/Getty Activists protest Donald Trump's proposed Muslim ban People listen to speakers at a demonstration against racism and conservative presidential candidate Donald Trump's recent remarks concerning Muslims on December 10, 2015 in New York City. Dozens or demonstrators and activists converged at Columbus Circle to denounce the politics of Trump and the treatment of Muslim refugees both in America and Europe. Spencer Platt/Getty Activists protest Donald Trump's proposed Muslim ban People listen to speakers at a demonstration against racism and conservative presidential candidate Donald Trump's recent remarks concerning Muslims on December 10, 2015 in New York City. Dozens or demonstrators and activists converged at Columbus Circle to denounce the politics of Trump and the treatment of Muslim refugees both in America and Europe. Spencer Platt/Getty Activists protest Donald Trump's proposed Muslim ban People listen to speakers at a demonstration against racism and conservative presidential candidate Donald Trump's recent remarks concerning Muslims on December 10, 2015 in New York City. Dozens or demonstrators and activists converged at Columbus Circle to denounce the politics of Trump and the treatment of Muslim refugees both in America and Europe. Spencer Platt/Getty

Often sporting bow-ties with his black robes, Judge Robart is known for saying from the bench in 2016 that “black lives matter.” He cited the statement popularised 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, Judge 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,” Judge Robart wrote in that opinion, “the balance of hardships tips in the favour of preventing human suffering.”

Adkins said he thought his friend would be able to take Mr Trump's attacks in stride.

“His view is that criticism is important,” said Mr Adkins.