MORE AND MORE, the campaign trails are leading into court. The campaign-financing laws, the Federal Election Commission's rules and the Supreme Court's pronouncements have generated lots of controversies about exactly what politically active people and groups may do. The courts are being called on to resolve, with increasing precision, a mass of important and rather ungainly problems of political rights.

Most conspicous in the legal maneuvering is the elbowing for advantage among labor and business groups. Labor suffered a setback last week when Federal District Judge Oliver Gasch told the National Education Association to stop collecting political donations from some members by a "reverse checkoff." That involves making payroll deductions automatically unless a member objects. Unions have hoped to use the technique to fatten their political-action funds. But Judge Gasch ruled - correctly, in our view - that the method does not ensure that funds are given knowingly, and undermines members' right not to participate. The union, he held, must let each member approve or veto the deductions in advance.

On the corporate side, the outlook is more bullish. A number of companies and industry groups have challenged the tight curbs on their political spending and soliciting. Now the Supreme Court decision that corporations have some political rights has opened up areas of contention that most people, including ourselves, had regarded as closed. Before long, the courts will no doubt have todecide whether companies and trade associations may still be barred from spending in behalf of candidates. If corporate money is allowed to flood freely into national politics, the consequences could be immense - though probably not so predicatble as some may think.

The Republican National Committee and the Ripon Society are taking two other tacks in challenging the system of public financing of presidential general-electio campaigns. First, they argue that the ban on coordinated private efforts, a condition of public financing, unconstitutionally resticts individual's political activities. Second, they maintain that barring private donations and keeping public spending so low inhibit grass-roots activity and give an unfair advantage to incumbents and candidates backed by unions - whose political efforts are nt severely curbed.

The Republicans may have reason to gripe about the edge that incumbents and labor-supported candidates enjoy. But those are mainly political problems, not constitutional ones. In our view, however, there is reason for legal and political concern about the ban on private donations to presidential campaigns. Last time around, grass-roots activity did suffer. It was almost impossible for a congressional candidate to affiliate with a presidential ticket without running afoul of the law. If the aim of campaign regulation is to curb the advantage of large, well-financed groups, and give individuals a greater voice in politics, those restrictions need to be reassessed.