Criminal charges against an American man who modified his Maserati to resemble a Decepticon from the Transformers films have been dropped after a judge decided he was not “impersonating police”.

It is unclear whether officers in Braintree, Massachusetts, understood the meaning of the car’s decoration when pulling the driver over on 9 August.

Police argued that the man was deliberately impersonating police and was a legitimate threat to public safety but the judge ruled that the vehicle’s appearance did not constitute a crime.

Lawyer Russell Matson, who represented the unnamed driver, called the ruling on Thursday at Quincy District Court a “victory for common sense over police authority”.

He said a few days before being stopped, his client had wrapped or “dipped” his car to appear as Barricade, one of the evil Decepticon robots from the 2007 Transformers film.

The luxury 2010 Maserati GranTurismo was coated in black and white, with police-style identity numbers and “speed enforcement” written on the rear bumper.

But instead of the slogan “protect and serve”, “Decepticons punish and enslave” was emblazoned on the white car door.

In the Transformers comic book series, Decepticons are the enemies of Autobots – robot aliens who protect humanity.

They transform into everyday vehicles to conceal themselves on Earth, such as the police car.

Mr Matson said his client never represented himself as a police officer or attempted to pull anyone over.

“The car itself, while certainly distinctive, did not have any blue lights like an actual police car,” he added.

“Despite decoration that makes it look similar to a police car, it does not bear any official town or state seal of any police department.

“The statute for impersonating a police officer states that a person must ‘act as such or require a person to aid or assist him in a matter pertaining to the duty of such an officer’.