Unless Congress acts, the U.S. Forest Service faces a problem. A federal judge in Southern California has said the agency cannot require forest passes for those who do not use such amenities as picnic tables or toilets.

Doing so, Judge Terry Hatter said last week, amounts to a parking fee and the courts have already said the agency cannot charge someone for the privilege of parking. The ruling leaves the Forest Service with something of a problem, or, more correctly, several of them.

Without a change in the law, the agency must either give up the fees or find some way of deciding which vehicles belong to which sort of visitor.

There are other problems, as well. Knowing that they may park for free if they don’t use amenities could encourage forest visitors not to use them — and to leave in their wake trash and even human waste.

Nor does it make sense to require the agency to build two parking lots in popular places, one for those who use amenities and one for those who don’t. Parking roadside is no answer. Forest roads are not four-lane highways, and cars alongside them could create a safety hazard.

Finally, fees go for things forest users want — parking lots, toilets and picnic tables, even things like trash pickup. While the Forest Service does collect more than is required for simple maintenance and the like, much of the extra goes to improve and add facilities. In places like the Deschutes, where demand is heavy, those fees are critical to ensuring there will be places to park, picnic and even access trails.

Congress can correct the problem in fairly short order. It simply needs to approve a law saying that, yes, it did intend to require everyone who uses the forest, including those who simply park there, to pick up part of the tab to keep the forest in good shape.

Doing so wouldn’t add to the nation’s tax burden or decrease national security or invade personal privacy. It simply would guarantee that the Forest Service, strapped for cash as it is, can keep the national forests clean and attractive places to visit.