CONCORD, N.H. — Ski areas cannot be held liable for negligence in slope side collision cases, even if an employee causes the accident, the New Hampshire Supreme Court ruled Wednesday.

The court unanimously ruled against Diana Martinez of Chelmsford, Massachusetts, who sued Gunstock ski area after a snowboard instructor crashed into her from behind four years ago.

The justices upheld a lower court’s dismissal of the negligence suit that Martinez filed, in which she claimed she suffered head injuries in the accident. The justices ruled that state law exempts ski areas from liability and says skiers and snowboarders assume the risks and hazards of participating in the sport.

The ruling is the state’s first to address ski area liability when an employee is involved, said Gunstock’s lawyer, Tom Quarles.

“It was an undecided area of New Hampshire law under the ski statute until now,” Quarles said. “With the overlay here of the allegedly offending skier being a ski area employee, the court says you can’t use that hook to get around ski area immunity for skier-skier collisions.”

Gunstock disputed whether the snowboard instructor was actually working for the ski area at the time of the 2010 collision, but the court said it wouldn’t have mattered. The law applies in all person-to-person collisions on the slopes, the justices ruled.

“The legislature intended to include, as a category of inherent risk, collisions with ski area employees, regardless of whether they were working at the time of the collision,” Justice Carol Ann Conboy wrote.

Martinez claimed Gunstock failed to adequately train and supervise the instructor, who is not named in the ruling. Her lawyer, Phil McLaughlin, declined to comment on the ruling.

Quarles said the ruling is specific to New Hampshire law, and that ski area liability laws in other states may differ.