A fresh inquest has been ordered into the death of Pte Cheryl James who died at Deepcut barracks in 1995.
The 18-year-old was found with a single gun wound to the head.
An earlier inquest into her death recorded an open verdict, but two High Court judges quashed that on Friday due to "an insufficiency of inquiry".
Judge Peter Thornton QC said "the discovery of new facts or evidence" made "a fresh investigation, including a fresh inquest, necessary or desirable in the interests of justice".
Des and Doreen James applied for a new inquest after the Human Rights Act was used to get access to documents about their daughter's death.
"When young people die in violent circumstances, a rigorous and transparent investigation should be automatic," they said in a statement.
"Something went dreadfully wrong at Deepcut, yet until now no-one has bothered to look at how and why our daughter died.
"We can only hope that Cheryl's legacy helps change the current ineffective and discredited military justice system."
Pte James was one of four soldiers who died at the barracks in Surrey between 1995 and 2002, as claims of bullying and abuse emerged.
Privates Sean Benton, James Collinson and Geoff Gray also died from gunshot wounds.
Pte James was found in a small wooded area close to the gate where she had been posted, alone.
In the subsequent investigation, the fragmented bullet from her head was not examined and was later lost. Also lost were the bullet's casing, other bullets in the rifle, and Pte James's clothing.
"Her rifle was not examined forensically. No fingerprints were taken from it. No gunshot residue tests were made," Judge Thornton said.