US Chief Justice Roberts underscores defence of judiciary amid Trump's attacks

US Chief Justice John Roberts underscored his defence of the American judiciary on Wednesday amid verbal attacks by President Donald Trump and his allies on judges who have impeded aspects of his sweeping agenda, again stating that impeachment is an inappropriate response to unfavourable rulings.

Trump, some fellow Republicans in the House of Representatives and his billionaire adviser Elon Musk have advocated impeaching some of the judges who have issued decisions against the president's policies since he returned to office in January, a process in Congress that could lead to removal from the bench.

"Impeachment is not how you register disagreement with decisions," Roberts said during remarks at a judicial event in Buffalo, New York.

Roberts, who leads the Supreme Court and its 6-3 conservative majority, did not mention Trump by name. But his comments echoed the rare rebuke issued by Roberts of the president in March after Trump called for the impeachment of a judge who had ordered his administration to halt the removal of Venezuelan migrants under a 1798 law called the Alien Enemies Act. Trump also labelled the judge a "Radical Left Lunatic."

The Supreme Court increasingly is being called upon to intervene in major legal disputes involving the president, whose aggressive agenda and flurry of executive orders often have been stymied by lower courts.

Critics have accused the administration of defying lower court orders and even a Supreme Court ruling involving Trump's crackdown on immigration.

Roberts on Wednesday indicated that the appeals process - not impeachment - is the proper way to deal with adverse rulings.

"That's what we're there for," Roberts said, answering questions posed by a federal judge before an audience of lawyers and other members of the judiciary.

Roberts, who was born in Buffalo and raised in Indiana, also spoke about the importance of the independence of judges in the US system of government that separates the powers of the president, Congress and the judiciary.

"This job is to obviously decide cases, but in the course of that, to check the excesses of Congress or the executive, and that does require a degree of independence," Roberts said, drawing applause from the crowd.

Roberts engaged in a wide-ranging conversation addressing numerous subjects including the relationship among the court's nine justices, which he said were strong despite sometimes sharp words exchanged by those in the majority and in dissent in major cases. Members of the court's conservative and liberal blocs often are on opposite sides in the most important decisions.

Trump's administration is contending with more than 200 lawsuits challenging his policies. His Justice Department has in turn flooded the Supreme Court with requests seeking emergency relief to enforce his policies. It has filed 13 such requests in just over 15 weeks since Trump returned to office.

That number is unprecedented and shows no signs of abating, Georgetown University law professor Stephen Vladeck, who has studied the Supreme Court's emergency docket, wrote in a blog post.

The court on Tuesday handed Trump a major victory when it allowed his ban on transgender people serving in the military to take effect. It also has permitted the administration to cut millions of dollars in teacher training grants - part of Trump's crackdown on diversity, equity and inclusion initiatives - and to fire thousands of probationary employees as he moves to slash the federal workforce.

The justices, however, declined to let the administration withhold payment to foreign aid organizations for work they already performed for the government, and required it to "facilitate" the release from custody in El Salvador of a man wrongly deported to that country.

The justices also issued a decision to halt deportations of Venezuelan migrants to El Salvador under the Alien Enemies Act after lawyers reported that the government was poised to imminently remove some in violation of the Supreme Court's prior order.

The court is scheduled to hear arguments on May 15 in Trump's bid to broadly enforce his executive order to restrict automatic birthright citizenship.