By Scott Malone

BOSTON (Reuters) - A New Hampshire man has the right to drive around the New England state with a license plate reading "COPSLIE," the state's top court ruled on Wednesday.

The state Supreme Court upheld a challenge to Department of Motor Vehicles' rules, finding they were unconstitutionally broad by allowing officials to deny requests for vanity license plates that "a reasonable person would find offensive to good taste."

The man, who in 2012 legally changed his name to "human" from David Montenegro, requested the plate in 2010 and sued the state when it denied his request, instead offering a place with his second choice, "GR8GOVT."

The court ruled that rules based on standards of taste were too broad and therefore likely to be used arbitrarily or in a discriminatory fashion.

"We question whether prohibition of accusations of moral turpitude would constitute 'viewpoint-neutral' regulation," three justices wrote in a decision sending the matter back to a lower court in the state, whose motto is "Live Free or Die."

The state attorney general's office had defended the DMV in this case, arguing that the main purpose of license plates was to help identify vehicles, not to serve as a platform for political expression.

State officials could not be reached for immediate comment on Wednesday.

"This opinion today is about keeping the government honest and fair when it regulates speech," said Anthony Galdieri, an attorney with Nixon Peabody who represented the man.

Gilles Bissonnette, legal director for the New Hampshire Civil Liberties Union, which also backed the case, called the decision an important protection of political speech.

"This message is one that's inherently political and one of the most fundamental doctrines in understanding free-speech cases is that we respect and appreciate political speech," Bissonnette said. "Unfortunately, what took place here is that the DMV regulation, which is incapable of any objective interpretation, was used to discriminate against human because of his speech."

(Reporting by Scott Malone and G Crosse)