By Jonathan Stempel

(Reuters) - The New Jersey Supreme Court on Tuesday ruled that a state law protecting employees from discrimination on the basis of marital status covers people who are separated, in the process of divorcing or divorced.

By a 6-0 vote, the court said employers cannot discipline, block the advancement of or fire workers whose marital status they may disapprove of or be concerned about, when it has no bearing on job performance or the workplace environment.

It said the state's Law Against Discrimination also bars discriminating against current or prospective employees because they are single, married, or moving from one to the other.

"An employer may not assume, based on invidious stereotypes, that an employee will be disruptive or ineffective simply because of life decisions such as a marriage or divorce," Judge Mary Catherine Cuff wrote for the court.

The decision upheld a 2014 ruling by a mid-level state appeals court in favor of Robert Smith, a certified emergency medical technician who had worked for 17 years for the Millville Rescue Squad, a medical transportation provider.

Smith was fired as director of operations in February 2006 after he had had an affair with a volunteer worker and told his supervisor John Redden that his marriage was collapsing, leading Redden to say he believed an "ugly divorce" would follow.

A trial judge had dismissed Smith's lawsuit, but the Supreme Court said a reasonable jury could find that "discriminatory animus" against divorcing employees was a factor in his firing.

The Supreme Court returned the case to the trial court. Smith is seeking damages, including for loss of income.

"It's a good decision," his lawyer Mario Iavicoli said in a phone interview. "If you're going through a divorce and it's not affecting your job at all, how can you fire somebody?"

A lawyer for the Millville Rescue Squad and Redden did not immediately respond to requests for comment.

Millville is located in southern New Jersey, about 45 miles (72 km) south of Philadelphia.

The case is Smith v Millville Rescue Squad et al, New Jersey Supreme Court, No. A-19-14.

(Reporting by Jonathan Stempel in New York; Editing by Bernard Orr)