US President Barack Obama has suffered a setback in his plan to spare millions of people living illegally in the US from deportation after the Supreme Court blocked his reforms.
The Supreme Court has announced it is split on the plan, which comes as a blow to the president's 2014 executive action which he enacted without Congress and will now be assessed in a lower court.
Republican House Speaker Paul Ryan applauded the news, saying only Congress should write laws.
But the president said the deadlock was "heartbreaking" for millions of people.
"They are Americans in every way but on paper," he said at the White House, adding that reform will happen, sooner or later.
"Congress is not going to be able to ignore America forever," he said.
Texas led 26 Republican-led states in challenging the programme, which would have given the right to work to millions of people.
The deadlock between the eight judges was only possible because of the death of the ninth, Justice Antonin Scalia, leaving a vacancy that is still unfilled.
This is the first tied decision produced by the court, as the Senate continues to block Mr Obama's nominee, Judge Merrick Garland.
The Deferred Action for Childhood Arrivals (DACA) and the Deferred Action for Parents of Americans (DAPA) initiatives had been on hold since 2015 as the court considered the programmes' legality.
DAPA was considered particularly controversial as it allows the parents of US citizens and permanent residents to remain in the county for up to three years and apply for work permits.
Lawyers for the state of Texas argued that state governments would be overburdened by having to spend more on public services with the addition of the undocumented residents.
The lack of ruling leaves the legal status of about four million undocumented immigrants in limbo.
President Obama's unilateral action would have allowed migrants to obtain work permits and would block them from deportation while their citizenship status was being determined by lawmakers.
Democratic candidate Hillary Clinton called the courts deadlocked opinion "unacceptable" and said that immigrants "enrich our communities and contribute to our economy every day".
"We should be doing everything possible under the law to provide them relief from the spectre of deportation," Mrs Clinton said in a statement.
Republican lawmaker Paul Ryan applauded the Supreme Court for making "the president's executive action on immigration null and void".
"The Constitution is clear: The president is not permitted to write laws, only Congress is."
Mr Ryan, the top-ranking elected Republican, is at odds with the party's presidential nominee-to-be Donald Trump over his plans to build a wall on the southern border paid for by Mexico.