Massachusetts has nixed Uber’s use of a GPS-based metering system. (Linda Davidson/The Washington Post)

Since Uber came into D.C. in December and quickly butted heads with taxi regulators, the upscale app-based car service has protested that the District’s aggressive treatment is an anomaly. Aside from some brief troubles in California, they’ve argued, Uber has largely avoided regulatory scrutiny in the more than a dozen other cities it serves.

But now Uber’s run into a new spot of regulatory trouble, up the Eastern seaboard. Six months after the D.C. Taxicab Commission ticketed an Uber driver in a sting operation, the city of Cambridge, Mass., did the same, and a state agency has since ruled its metering system illegal, threatening Uber’s operations in the greater Boston area.

In late May, Cambridge officials took an Uber ride, then afterward ticketed the driver for operating an unlicensed livery service and using a unlicensed measuring device.

Uber appealed the latter charge to the Massachusetts Division of Standards, arguing that Uber’s GPS-based metering system is sufficiently accurate. Last week, however, the agency rejected Uber’s appeal.

”The major problem at this time is the fact that there are no established measurement standards for its current application and use in determining transportation costs similar to that of approved measurement systems for taximeters and odometers,” the agency’s director, Charles H. Carroll, wrote.

D.C.’s top regulator, Taxicab Commission Chairman Ron M. Linton, has raised similar concerns about the reliability of Uber’s metering, albeit less formally.

The upshot, for Uber, is that in the eyes of Massachusetts, its metering system is a no-go: “[T]he use of the unapproved GPS system to assess transportation charges must be discontinued until such time as the standards for its use are established” by the National Council on Weights and Measures and the National Institute of Standards and Technology, the director wrote.

Getting standards established by those national bodies is not a swift or simple proposition. And until that happens or the Commonwealth of Massachusetts changes its mind, that means Uber’s business model is missing a key part: A low-cost, low-hassle metering system that requires participating drivers to have only a smartphone rather than an expensive, custom-installed meter.

Officials in Cambridge have not yet responded to calls for comment. Travis Kalanick, Uber’s CEO, said Thursday that business continues as usual in Boston and its environs while the company decides how to respond to the decision.

”We’re not getting complaints about people who are not being charged properly.” he said. “You can imagine who are the loudest people questioning this. It’s not the riders, I’ll tell you that much.”

Uber is exploring its “political as well as legal options,” Kalanick said. “On the political side, it will be on the the elected and appointed officials in the state of Massachusetts to make up their minds if they’re going to support innovation or not,” he added.

UPDATE, 8/16: Gov. Deval Patrick’s administration announced on Wednesday that the ruling has been reversed and Uber is free to continue doing business in the Bay State.

Here’s the original state ruling: