IN A WELCOME CLARIFICATION of the District's home-rule authority, the D.C. Court of Appeals has now upheld the city's strict gun-control law. This surely won't be the last legal test of the law, since the National Rifle Association has indicated that it won't rest until the Supreme Court has spoken on the local issue. But while we're waiting, there remains the question of how the law has been working so far. Is the city any safer?

Yes. There are some encouraging signs that it is. But whether this is the direct result of tough gun controls is questionable. For example, the police department reports that the number of crimes involving guns has decreased, as has the number of guns confiscated. That's good - but the total number of "crimes against persons" also has been decreasing which would tend to account for the other decreases. Also, say the police, the number of registered guns retrieved is minimal.

So it could be argued - and always is by the NRA and its friends - that even this tough law (which prohibits the possession of handguns by anyone other than police officers, security guards or citizens who purchased their guns before September, 1976 and registered them before February, 1977) is not accomplishing much. Besides, criminals don't seem to have any trouble getting guns - and can hardly be said to be registering them.

True. Reports regularly show that Virginia is the largest source of firearms used in Washington-area crimes and - no surprise - Maryland is second. In the absence of strong national gun controls, some uniform regional controls would help. Yet in Arlington County only this summer, an effort by county board member Joseph S. Wholey to outlaw any handguns not registered with police failed when another member, John Purdy - who had previously supported a regional ordinance - joined opponents in killing the measure.

In the narrowest sense, then, gun controls in the District aren't working. They are but a start in the region. And the failure of neighboring jurisdictions to curb gun traffic is no reason to rescind the city's law. Besides, it isn't just the criminals' guns that are dangerous. We like to believe that the city's handgun ban is reducing the possibility of accidents in homes. And that in itself is ample justification for keeping this sensible public-safety measure on the books and working for similar protections throughout the Washington area.