District Crossfit owner and trainer Andrew Killion in a personal training session with Dominique Evans last month. (Linda Davidson/The Washington Post)

A SURPRISING one out of every four U.S. jobs requires a license of some kind. Excessive regulation of the labor market through mandatory credentialing has turned into a subtle destroyer of jobs and opportunity, according to a recent White House report, which urged state and local governments to roll back unnecessary rules and resist onerous new ones. Based on recent events in the District, we’d say officials either didn’t get the memo — or they need to give it a closer reading.

Fitness clubs are popping up all over the city, staffed by personal trainers who help clients grunt and squat their way to slimmer waistlines and buffer abs. This does not appear to have produced a wave of injuries or other issues, much less any problems clearly traceable to the lack of city-mandated credentials. Nevertheless, the D.C. Council passed (and then-Mayor Vincent C. Gray, a Democrat, signed) a measure last year that requires all personal trainers to “register with the Mayor on forms prescribed by the Mayor . . . and pay the registration fee established by the Mayor.”

The task of fleshing out such crucial details as the definition of a “personal fitness trainer,” and the amount of the registration fee, was delegated to the little-known Board of Physical Therapy, a licensing agency under the D.C. Department of Health whose members mostly are physical therapists. Predictably, and not unreasonably, all sorts of fitness and exercise operators have objected, sensing a protectionist plot by the physical therapists — suspicions that only grew when an early draft regulation suggested making a four-year college degree prerequisite to registration as a personal trainer.

That proposal has been withdrawn, but it’s far from clear what the board will, indeed, come up with next month, when it finishes draft regulations and sends them to the executive branch for vetting, before a 30-day public comment period. What is clear is that the White House report identified best practices for occupational licensing — and the District ought to follow them. Specifically, agencies should clearly document the health or safety necessity of any new licensing or registration requirements, and subject them to rigorous cost-benefit analysis, before acting. They should minimize the time and expense involved in obtaining credentials. And new licensing or registration requirements should sunset every few years to prevent outmoded standards from congealing into permanent law. Mandatory insurance or bonding is often a more efficient means of consumer protection than licensing, the White House report noted.

Perhaps a bare-bones public registry of personal trainers, listing their formal training and experience, and paid for by modest fees, might enable consumers to make better choices. It’s equally conceivable that it won’t. What’s all too thinkable is that the District will be the first jurisdiction in the United States to write heavy-handed personal trainer regulations, squelching a lot of productive activity while producing no particular gain to anyone except incumbent competitors.