The three-year suspended jail sentence was delivered as the British government seeks to push ahead with legislation to introduce an amnesty to former soldiers and individuals involved in decades of sectarian violence that killed around 3,600 people.
David Holden, who was 18 at the time, admitted to firing the shot but said his finger slipped on the trigger when Aidan McAnespie, 23, passed a border security checkpoint in county Tyrone on his way to a Gaelic football match.
Holden was found guilty of manslaughter in November after the judge found he gave a "deliberately false account" of events.
Relatives of the victim outside Belfast Crown Court said they would have preferred a custodial sentence, but that they were comforted by the guilty verdict and the fact the killing had been given due legal process.
"The opportunity to have a court case where evidence is shared in open court - people can argue about it - that is an important part of the healing process," said Holden's cousin, Brian Gormley.
"That has given us some solace," he said. "All families should have access to that."
The British government's amnesty legislation, which is being debated in the upper house of parliament, has been strongly criticised by victims' rights groups, all Northern Ireland political parties and the Irish government.
UN High Commissioner for Human Rights Volker Turk said this month that the draft legislation appears to be incompatible with Britain's international human rights obligations, even after London introduced some amendments to try and address concerns.
(Reporting by Amanda Ferguson; Writing by Padraic Halpin and Conor Humphries; Editing by Andrew Cawthorne, Alexandra Hudson)
By Amanda Ferguson
