Federal judges across the country-including the Chief Justice of the United States-withheld disclosures about their personal finances at the last minute yesterday after six southern colleagues obtained an extraordinary court order to block a new ethics law.

The southern judges-from Alabama, Georgia, Louisiana and Texas-won a temporary restraining order to hold up compliance by the judicial branch of government.

"In this unfortunate period when kidnapings are daily news," the judges asserted in seeking the order, "the public disclosure of the details of the judges' finances invites disaster."

The ruling issued in New Orleans by U.S. District Judge Robert collins, triggered a late-afternoon halt to judicial filings required by the Ethics in Government Act of 1978.

The order was directed to clerks of all federal courts, including Michael Rodak at the Supreme Court. He learned of it after he had sent the court press office copies of the filings of six of the nine justices.

At 4:30 p.m., he relayed word to reporters that they would not receive the filings that would not receive the filings that had been expected within a half-hour from Chief Justice Warren E. Burger and associate Justice William H. Rehnquist. Justice Lewis F. Powell Jr., who has been ill, had been granted an extension previously.

How can a district judge issue an order to the Supreme Court? a reporter inquired. "That's a good question," Rodak replied. But he said he had "no choice"-at least for the ment-except to comply.

Rodak said Burger had been told of the order in a visit by Judge Edward A Tamm of the U.S. Court of Appeals here. Tamm is chairman of the Judicial Ethics Committee, which is charged with receiving the reports of the federal judiciary.

Court press officer Barrett McGurn said he assumed there would be "a quick appeal," but could not say who might file it. At the Justice Department, a spokesman said that the order will be studied, after a copy is in hand, to see what action may be appropriate.

The new ethics law, which took effect yesterday, requires detailed financial disclosures from about 11,000 federal officials and judges whose salaries are $44,700 or more a year.

At the U.S. District Courthouse here, clerks of the appeals and district courts, who had been planning to make the financial statements of their judges available today, said that they would abide by the restraining order and not make the statements public until the issue is resolved.

Both George A. Fisher, circuit court clerk, and James F. Davey, district court clerk, said they were acting after speaking to Judge Tamm. The clerks both said Tamm had informed them of the ruling and told them that it applied to court clerks as well as to the committee Tamm heads.

Tamm also ordered the Temporary Emergency Court of Appeals, where some statements already had been sent, to put a hold on further release.

The southern judges who filed the lawsuit were Adrian Duplantier, New Orleans; Nauman Scott, Alexandria, La.; Earl Veron, Lake Charles, La.; Robert Hill, Dallas; Wilbur Owens, Atlanta, and Robert E. Varner, Montgomery, Ala.

In their lawsuit, they maintained that for Congress to have included judges under the ehtics law was "an unconstitutional encroachment upon the separation of powers in the federal government."

The judges also protested that the law puts them in a dilemma; if they refuse to comply, the public will doubt their integrity; if thy do comply, they face possible threats of economic and physical harm from disgruntled defendants who appear in their courtrooms.

The six Supreme Court filings that were made public revealed wide variations in the wealth of the justices, whose annual salary is $72,500. Burger's salary is $75,000.

At the low end of the scale is Justice Thurgood Marshall, whose only outside income-interest from a savings account-was in the under-$1,000 category. He listed a liability-a promissory note to an otherwise unidentified "Paul Moore"-in the $5,000 to $15,000 scale.

At the top end of the scale is Justice Potter Stewart, who, with his wife, listed assets, other than their home, valued between $1,265,000 and at least $2,180,000. The assets include Mrs. Stewart's shares in three trusts, with each share worth at least $250,000, and the justice's stake in a trust in the $100,000-$250,000 bracket. Last year, the trusts alone yielded income in a range of $62,500 to $135,000.

When his appointment was confirmed in 1971, Justice Powell also put himself in the millionaire category.

Modest holdings were disclosed by Justices William J. Brennan Jr., Byron R. White and John Paul Stevens. Justice Harry A. Blackmun listed listed fairly substantial assets, including five blocks of stocks and other securities worth $15,000 to $50,000 each.