WASHINGTON - In a victory for unions, the National Labor Relations Board ruled Thursday that employees can use their company e-mail accounts for union organizing and other workplace-related purposes, if they do it on their own time.

Once an employer gives an employee access to the company e-mail system, then the business cannot restrict what the employee e-mails, so long as it is generally workplace-related and isn't during working hours, the NLRB ruled.

The NLRB is a government agency that investigates unfair labor practices.

The ruling said that "the use of e-mail as a common form of workplace communications has expanded dramatically in recent years."

The ruling could give unions a powerful organizing weapon.

The three Democrats on the five-member board voted "yes," while the two Republicans abstained.

Decision reversed

The ruling reverses a 2007 board decision that employees don't have a legal right to use their employers' e-mail for union activity or discussing wages or other workplace issues.

It also upholds an opinion by the NLRB's general counsel, who suggested that workers had a presumed statutory right to use company e-mail to discuss a range of workplace issues - so long as they did it on their own time and unless an employer could demonstrate that doing so would hurt productivity or office discipline.

The decision was a victory for the Communications Workers of America, which brought the case in 2012 after it was unable to use company e-mail to organize employees of Purple Communications in Rocklin, Calif., a company that provides interpreting services for the deaf and hard of hearing. The union contended that prohibiting Purple workers from using company e-mail to organize interfered with its efforts.

'Victory for workers'

Bernie Lunzer, president of the Newspaper Guild-CWA and a vice president of the Communications Workers of America, called the ruling "a big victory for workers in general."

Joel Barras, a lawyer who represents employers in collective bargaining and labor arbitration matters, said that the NLRB in its ruling "once again elevated employee protected activity over employer property rights. Not only will employees now have the ability to use their work e-mails in their efforts to unionize or discuss terms and conditions of employment with coworkers, an employer's communication system may also become an incredibly effective tool used to recruit members to form or join class-action cases."