The Senate yesterday approved legislation that could greatly increase the power of the courts to overturn actions by federal regulatory agencies. The vote was this Congress' strongest anti-regulatory action to date.

The measure, an amendment attached to a housekeeping bill known as the Judicial Improvements Act, would let courts overturn regulatory agencies whenever they thought the agencies had interpreted the law incorrectly.

Currently, they may overturn them only for acting arbitrarily, capriciously or in some other extreme way. Agency rules are otherwise presumed to be valid.

The amendment was sponsored by Sen. Dale Bumpers (D-Ark.). It passed on a voice vote after an attempt to kill it failed, 51 to 27.

The amendment would affect the entire spectrum of government activity from environmental, health and safety standards to communications rules, freight rates and agricultural and economic regulations.

Sen. Edmund S. Muskie (D-Maine), while agreeing that regulations should be curtailed, said the Bumpers amendment "could stop the federal government in its tracks."

"It says that federal regulations are not worth the paper they are written on. They would be accorded no respect at all until a federal court rules they are acceptable," he said.

Bumpers, however, defended his measure as redressing decades of pass wrong. "Age-old case-law precedents have presumed an expertise on the part of regulation writers," he said. "So every time a citizen wants to challenge a regulation, he must assume the burden of proof. My bill would make it a fair fight for people being regulated."

The amendment adds this language to the Administrative Procedure Act: "There shall be no presumption that any rule or regulation of any agency is valid. And whenever the validity of any such rule or regulation is drawn in question in any court of the U.S. or any state, the court shall not uphold the validity of such regulation unless such validity is established by a preponderance of the evidence shown."

Bumpers speculated that if his amendment is passed by the House and is signed by the president, "Regulation writers will have to be more circumspect. Appeals courts will not be able to rubberstamp agency decisions. It gives courts the duty to look at the record and quit deferring to so-called expertise."

He acknowledged that the change would make it easier for industry to challenge environmental and safety regulations, for example, and that many issues previously resolved in court could be reopened.

Bumpers first introduced the change in 1975, but it was widely opposed by administrative law experts, and had remained bottled up in the Judiciary Committee.

The Carter administration has opposed the bill, although Bumpers claimed it has the support of former attorney general Griffin B. Bell.

Bumpers said he does not expect a favorable reception for the proposal in the House Judiciary Committee, but predicted that it would pass on the House floor."I've got a lot of homework to do," he said.

While contending that "I'm not one of those knee-jerk anti-regulators," Bumpers said agencies have "run amok with regulation writing." He cited a Department of Agriculture regulation of cattle auction rates. "That's like saying how much Baskin Robbins can charge for an ice cream cone."

The Bumpers amendment is one of several anti-regulation measures Congress has been considering. Another, the one-house veto, would allow the Senate or the House to reject any agency regulation.

Bumpers said he opposes the veto bill because "we're not exercising our oversight responsibilities as it is. We couldn't come close to wading through all those regulations."