The Trump administration urged the Supreme Court today to dismiss two cases challenging its revised travel ban, issued in March, saying they are moot in light of recent developments. But the plaintiffs urged the justices to decide the cases notwithstanding recent changes in the scope and duration of the travel restrictions.

The court had been set to hear arguments in the case Oct. 10. But the justices removed the case from the argument calendar last month after the administration announced in a presidential proclamation that it would replace temporary travel restrictions issued in March that had limited travel from six predominantly Muslim countries for 90 days.

The new restrictions, which are set to take effect Oct. 18, apply in various ways to nine countries. Most citizens of Iran, Libya, Syria, Yemen, Somalia, Chad and North Korea will be banned from entering the United States, while citizens of Iraq and some groups of people in Venezuela will face restrictions or heightened scrutiny.

“A case is moot,” Solicitor General Noel J. Francisco wrote today, “when a challenged government regulation is replaced by one that is not substantially similar.”

The new restrictions are different from the earlier ones in important ways, he wrote, and were “based on detailed findings regarding the national security interests of the United States that were reached after a thorough, worldwide review and extensive consultation.”

A challenge to the new restrictions, Francisco wrote, “must proceed on its own terms and in the district court in the first instance.”

The American Civil Liberties Union has already challenged the latest order in a pending case in a federal court in Maryland. The addition of two countries that are not majority Muslim, the group said, did not cure the “original sin” of the earlier orders. All three orders, it said, were an effort to make good on President Donald Trump’s campaign pledge to institute a “Muslim ban.”

In its own Supreme Court filing today, the ACLU urged the justices to proceed.

“This case is not moot,” the group said. “Plaintiffs retain an all-too-real stake in the outcome of the case. The 90-day ban on their relatives has now been converted into an indefinite ban with the potential to separate their families, and thousands of others, for years.”

Lawyers for the state of Hawaii, which had also sued to block the March order, agreed.

“The parties retain a live dispute regarding the legality” of the order, they wrote. “Accordingly, this court should once again set the case for argument and adjudicate the legality of the president’s ongoing effort to usurp Congress’s power over immigration and unilaterally ban hundreds of millions of foreign nationals — the overwhelming majority of them Muslim — from the United States.”

Last month’s proclamation did not address a second aspect of the March order, which suspended the nation’s refugee program. That suspension was also at issue in the Supreme Court.

Francisco wrote that the administration will soon revise the restrictions on the refugee program, which are due to expire Oct. 24. That new action, he said, will also make that second part of the cases moot.

In addition to urging the Supreme Court to dismiss the cases, Francisco asked the justices to vacate the two appeals court decisions under appeal.

“If allowed to stand,” he wrote, “the lower courts’ decisions threaten to undermine the executive’s ability to deal with sensitive foreign policy issues in strategically important regions of the world.”

The plaintiffs in both cases urged the justices to let the appeals court decisions stand even if they dismiss the appeals from them.