A lawyer for relatives says suspects allegedly involved in the Kingsmill massacre should be named during an inquest.
"Suspects in this case ought not to have the benefit of hiding behind ciphers but rather their identities should be made public," said Alan Kane QC, for the families.
It follows a decision by a coroner in England to appeal against a ruling to identify suspects in the Birmingham pub bombings during inquests.
Lawyers in the Kingsmill inquest said the matter would probably go to the UK's highest court.
Ten Protestant workmen were shot dead by republicans in the incident in January 1976.
Alan Black was the sole survivor after suffering 18 gunshot wounds.
In January, former Sinn Fein MP for West Tyrone Barry McElduff resigned after he was criticised for tweeting a video with a loaf of Kingsmill bread on his head on the anniversary of the killings