THE SENATE has reacted in a curious way to what many of its members like to describe as the over-regulation of their constituents. Instead of doing something about the government agencies that do the regulating or taking back some of the power it has delegated to them, the Senate voted last week to give the job of curtailing those agencies to the federal appellate courts. It did this by adopting a proposal of Sen. Dale Bumpers to eliminate the presumption of validity that now cloaks agency rules when they are challenged in court.

On the surface, that sounds like a good idea. It would make the agencies justify their regulations before an impartial body, and this -- to hear the senators explain it -- would protect the public from bureaucratic over-reaching.

The trouble is that the agencies were created, at least in part, to get the judges out of the business of regulating the economy. And although this proposal would put them back in, its terms provide no protection against judicial over- or under-reaching -- a strange development in light of the constant criticism of the courts for judicial activism.

The presumption of validity with which agency rules are endowed came into existence because those rules are supposed to rest on the expertise an agency has built up over the years. There is something absurd, for example, about changing the law so that the Federal Power Commission must justify and explain from scratch its rules on high-voltage switching requirements and amperage regulations to a group of federal judges whose knowledge of such technical matters is scanty, at best.

There is, in addition, a real irony here in the fact that this proposal was attached by the Senate to a bill designed to make the federal court system more efficient and effective. But the Bumpers amendment would offset most of the streamlining provisions of the bill by generating a new kind of litigation in which the only sure winners would be the lawyers hired to carry it on.

If Congress wants to do something about over-regulation, it should start by looking at the laws it has passed instead of asking the courts to look at them. The flip side of bureaucratic over-regulation is legislative over-delegation. The real cure for that rests exclusively in the language of the laws Congress passes.