The decision of a federal court in California has cleared the way for an immediate confrontation between Congress and the executive branch over legislative vetoes. The court struck down one such veto on Christmas Eve, calling it unconstitutional, and President Carter seized that opportunity to say he will soon order all government agencies and departments to ignore the 150 or so other such vetoes Congress has passed in recent years.

Such an order is not likely to be accepted quietly on Capitol Hill. The legislative veto has become the darling of many congressmen who see it as a way of putting a leash on the federal bureaucracy. Content with the status quo, they have had no interest in seeking out a showdown over the constitutionality of the veto. Some of them even seem to have believed that the Reagan administration would not be so hostile to it. As a result, Mr. Carter's decision to ignore all those other veto provisions is open to the criticism that he is trying to force a showdown and to win a last-minute victory over some of his congressional foes.

The court decision, however, does cast a heavy shadow over almost every one of those other laws. It is the first time appellate judges have agreed with the argument that Congress cannot reserve to itself the right to overrule the administrative decisions it has delegated to executive branch agencies. That makes it, as Mr. Carter said, "profoundly significant" in the battle that has been running between Congress and every president since FDR.

It can be argued that President Carter would have been better advised to withhold a directive that all other veto provisions be ignored until this particular decision is affirmed or overturned by the Supreme Court. But there is a question as to whether this case is an appropriate one for the full review of legislative vetoes that his administration and others have sought for years.

By issuing his directive, President Carter has almost assured that some agency will act while he is still in office in a way to create a challenge to a legislative veto -- one that the justices cannot avoid. That is good. The legitimacy of the legislative veto is a question that needs to be settled, regardless of what the final decision is. The struggle between Capotol Hill and the White House has gone on too long, with too much confusion and gratuitous aggravation. A drastic step, like the one President Carter proposes to take, has been needed to force an end to it. Congress can then get on with the job of controlling the substance of administrative decisions instead of continually quarreling over the mechanism of control.