The UK and US have agreed to change an “anomaly” that has allowed Harry Dunn’s death suspect, Anne Sacoolas, to claim diplomatic immunity.
A court hearing last month learned that the “secret deal” allowed Ms Sacoolas to return to America after the 19-year-old died last August.
He was killed in an accident near RAF Croughton, Northamptonshire.
Speaking to the Press Association (PA), Harry’s mother Charlotte Charles said the change was a “huge step forward”.
She said the family’s campaign for Ms Sacoolas’ return to the UK will continue.