CONTRARY TO THE BELIEF of the judge who wrote it, this week's decision on federal coal leasing is a serious setback to President Carter's energy plan. Under the plan, the country is to double its coal production by 1985. That target was unrealistically high to begin with, and now Judge John H. Pratt of the Federal District Court here has forbidden any more coal leases until the environmental-impact statement is rewritten. The Interior Department fore sees a delay of one to two years.

The courtroom is the wrong place to settle these broad issues of energy and the environment. That is increasingly clear. The collision of values is real, and the questions being pressed by environmental advocates - like the four organizations who brought the coal-leasing suit - are important. They need to be heard and resolved. But the procedures of a civil suit are not well adapted to do it. They are designed to narrow the issues down to a few points, very often excluding, as in this case, matters of great national interest. The courts, in any event, are not well equipped to deal with the range of technical and economic controversy that environmental cases typically generate.

This disruption of the plans for coal leasing means that the country will have to import more oil over the coming years. Importing more oil means, in turn, increasing the country's dangerous dependence on foreign sources. Neither national security nor the ominous size of the U.S. trade deficit was an issue in the case before Judge Pratt. But they are certainly issues, and pressing ones, before President Carter as he develops American energy policy.

The evidence presented to Judge Pratt seemed to him to prove that the government has already leased more than enough coal-rich federal land to mining companies. That's why he concluded that an 18 month delay in leasing, to permit further environmental studies, would have no significant effect on actual coal production. He was counting tons of "potentially recoverable" coal, and the trouble is that some of it is inaccessible. Some is in checkerboard patches of leaseholds that will have to be filled out with new leases before it can be mined economically. Some of the old leases were granted under poor environmental contols, or none at all, and mining them would threaten far greater damage than the government today considers tolerable.

It's wrong, certainly, to heap all of the blame for this decision on the judge. Congress wrote the National Environmental Protection Act loosely, in a fashion that invites endless litigation. Government agencies - in this instance, the Interior Department - have not been uniformly skillful in responding to these suits. There has been a tendency to carry on the defense of departmental prerogatives rather than national interests. If this decision reflects no sense of the injunction's consequences as the Carter administration sees them, that is the administration's fault.

The new Department of Energy - which, incidentally, opens for business on Saturday - has an urgent responsibility to take hold of these suits and see to it that judges at least understand the President's purposes. The trade-offs are sometimes difficult. There is no such thing as strip mining without environmental damage.But there are good reasons to keep mining where the damage can be limited. Some of these reasons involve foreign policy and the protection of the American economy from foreign disruption, although you won't find mention of that kind of thing in an environmental-impact statement. A further 18 month delay now in leasing coal reserves is not a necessity but a luxury - to be bought at a price that no one can predict.