THE LEGAL SERVICES CORPORATION, created three years ago out of the remains of the "war on poverty," is turning out to be remarkably healthy. A congressional conference committee voted last week to increase its budget by more than 60 per cent next year - surely a sign that it is doing something right. And the House, after an extensive debate, agreed to remove some of the restrictions that have limited its work. But the corporation is still restrained by other troubling limitations and the Senate ought to delete them when it gets the opportunity later this month.

The corporation, you may recall grew out of a series of compromises. Those who believed that the government ought to make it possible for poor people to get the kind of legal services that others can buy accepted a long series of limitations on what the free services would be in order to get the bill out of Congress and past a threatened presidential veto. Several of those limitations were dropped this year by the House Judiciary Committee, but two of them were restored on the House floor and a new one added. These three, which seem particularly obnoxious to us, bar the corporation's lawyers from providing legal aid to poor people in matters concerning school desegregation, Indian rights and homosexual rights.

Underlying these restrictions is an obvious distaste of members of Congress for the substance of the right that some candidates for the corporation's assistance might want to assert. But that, it seems to us, is a strange test for Congress to apply. It is a test that says to the poor that, although they have the same rights as everyone else, they can exercise only those that Congress happens to believe in. As a matter of principle, lawyers who handle problems of the poor ought to be able to give them the same kind of help that they would give to paying clients; they ought not to be forced to say that they cannot handle a particular matter because Congress won't let them. That was the principle - despite the compromises - that lay behind the creation of the corporation three years ago, and it is one that deserves to be given its full dimensions now.