IT IS ALWAYS gratifying when help comes from an unexpected source. Senate liberals, led by Lowell Weicker (R-Conn.), have been waging a hard fought and so far unsuccessful fight against legislation that would restrict the jurisdiction of the federal courts in certain civil rights cases. In recent weeks, debate has centered on an amendment to the Justice Department authorization bill that would prevent courts from ordering busing beyond the neighborhood school in order to overcome segregation. Few senators have many good things to say about busing these days. The debate on this amendment focused on a broader question: is it wise to limit the remedies available to courts that seek to protect rights guaranteed in the Constitution?

Some were surprised when Sen. Barry Goldwater joined forces with traditional liberals to oppose the court-limiting move. But the argument he makes is essentially a conservative one. The founding fathers, he says, intended the judiciary to be independent. He quoted authorities dear to the heart of traditionalists --the Federalist Papers and the debates of the Constitutional Convention of 1787--to make his point. The framers of the Constitution, he points out, considered and rejected a proposal to grant Congress the authority to limit federal trial court jurisdiction of cases arising under the Constitution.

As for the appellate jurisdiction of the Supreme Court, where Congress does have power to make exceptions, Sen. Goldwater questions whether the legislature can grant review in a specific class of cases and then chip out narrow areas of these subjects solely for reasons of social policy.

If his fellow conservatives are not persuaded by the senator's historical and legal arguments on the powers of the respective branches of government, they should heed his words on the wisdom of measures that would limit the jurisdiction of the federal courts. "What we are talking about today," he said, "is not just a subject relating to a controversial issue that confronts school children and their parents at this moment of our history. The real question runs far deeper and affects the essence of our basic constitutional doctrines." He's right.