Lawyers for 14-year-old Kaylee McIntosh's parents Derek and Lesley said the Crown Counsel was in a "minority of one" after it emerged the Crown Office had ruled out anyone else being charged over the death in Loch Carnan, South Uist, in August 2007.
Major George McCallum, 52, was yesterday fined after he admitted contravening the Health and Safety at Work Act.
The prosecution at Inverness Sheriff Court had pushed for others to be charged and Sheriff William Taylor, QC, had indicated he favoured further action.
The Crown Office issued a statement saying Kaylee's death had been "tragic and avoidable" but had been the subject of a full inquiry involving the Health and Safety Executive, the police and the Crown.
Glen Millar, a partner in the McIntosh family's lawyers, Thompsons, said: "Setting aside that it is regrettable in the extreme it has taken over five years to reach that view, Crown Counsel is in a minority of one when it comes to assessment of the evidence and is at odds in that respect with sheriffs, senior counsel, Derek and Lesley McIntosh's legal team at Thompsons, as well as Derek and Lesley themselves. My instructions remain to write to the Lord Advocate, and no doubt he will provide a fuller explanation of the position, after which all options open to the family will be considered.''
A Crown Office spokesman said: "The Ministry of Defence is the subject of a censure issued by the Health and Safety Executive. Crown Counsel have concluded that on the available evidence there is insufficient evidence to prosecute any others involved in the death. Kaylee's parents have been advised of this decision."
Sentencing, Sheriff Taylor said the training exercise had been a "shambles which resulted in the death of a beautiful young woman".
Had Mr McCallum, of Peterhead, been involved in a similar chain of events today, he could have faced a two-year jail sentence. At the time of the tragedy, an unlimited fine was the maximum penalty.
A Fatal Accident Inquiry had established a catalogue of errors, from the craft being taken out in a force eight gale, for which it was not designed, to the failure to do a headcount after the capsize. The Marine Accident Investigation Branch also found Kaylee was wearing the wrong size of life jacket
Sheriff Taylor said of Mr McCallum: "He was one cog in a very much larger wheel. It is my hope matters won't end here."
He said there were senior officers who had not sought to establish if a proper risk assessment had been done beforehand.
He named Colonel David Taylor as having been in overall charge as commandant of the cadet camp and Major David Adams, who was in charge of the training programme for cadets.
Earlier, Mr and Mrs McIntosh, of Fyvie, Aberdeenshire, said: "No parent should have to endure what we have – the taking away of one so young and so dear for the very worst of reasons."