A federal judge on Saturday blocked the Trump administration from implementing a policy that would require immigrants to prove they have insurance or the financial resources for medical costs in order to obtain a visa.

The ruling, by Judge Michael Simon of the Federal District Court in Portland, Ore., was the latest in a string of court decisions to derail administration initiatives that would limit the admission of certain legal immigrants into the United States.

Judge Simon issued a nationwide temporary restraining order preventing the government from carrying out a proclamation by President Trump that would have gone into effect on Sunday.

Mr. Trump’s Oct. 4 proclamation ordered consular officers to bar immigrants who could not prove they had health insurance or the ability to pay for medical costs once they become permanent residents of the United States.