"No reasonable opportunities" within the gun licensing system could have stopped taxi driver Derrick Bird shooting 12 people dead, an independent review concluded today.
The report, ordered by Cumbria Constabulary, found that the mass killer lawfully held certificates for a side-by-side hammer action shotgun and a .22 rifle which he used to gun down his victims.
It said the force and other relevant agencies had no information prior to the rampage which showed the gunman should reasonably have had his certificates revoked and guns seized.
The force's firearms licensing procedures were "robust" and in line with the law and Home Office guidance, it added.
Bird, 52, killed 12 people, including his twin brother, David, and injured 11 others in a spree across West Cumbria on June 2 before turning his gun on himself.
Following the shootings, the Chief Constable of Cumbria Constabulary, Craig Mackey, ordered an inquiry into the force's issue of a shotgun certificate and firearms licence.
Mr Mackey also called for an assessment of its firearms licensing procedures involving the whole of the county.
In his review, the chairman of the Association of Chief Police Officers (Acpo) Firearms and Licensing Working Group, Adrian Whiting, said: "I have been able to assure the Chief Constable of Cumbria that the decisions made and the actions taken in respect of the grant and renewals of Derrick Bird's shotgun certificate, and those in respect of the grant of his firearm certificate, were in accordance with the law, regulation, Home Office advice and Acpo policy.
"I have concluded that the arrangements for firearm, shotgun and explosive certification in Cumbria are robust and that the people involved have the appropriate knowledge, skills and experience.
"In particular I consider that they are professional and committed to their work, and fully recognise the critical public safety issues at stake.
"There were no reasonable opportunities for the licensing system to have been the instrument of intervention to prevent the appalling offences subsequently committed."
The Assistant Chief Constable of Dorset Police continued: "The details of these circumstances do not give rise to any immediately obvious changes that need to be made, either in Cumbria Constabulary or in law, such as would have readily prevented the offences from being committed.
"There are a number of changes that may usefully improve public safety overall, but changes that would guarantee that offences of this nature could not be repeated would essentially require Parliament to approve much greater restriction on the private possession of firearms than is currently the case."
The report revealed that Bird had obtained a shotgun certificate in 1974 at the age of 16 and successfully applied for a firearms licence in 2007 for the .22 rifle.
In 1990 he was sentenced to six months in prison, suspended for a year, after he was convicted of two counts of theft and one count of handling stolen goods from his then employer, British Nuclear Fuels Limited.
Home Office guidance since 1969 has included advice that suspended sentences do not attract prohibited person status under the Firearms Act 1968.
Mr Whiting concluded that Bird had fulfilled all "necessary requirements for issue" and all appropriate inquiries were made, including home visits.
He pointed out that Bird unlawfully shortened the barrels of the shotgun in the hours before the first murder but there was no reasonable opportunity for the police to have become aware of this.
A separate review of the constabulary's firearms response on the day of the shootings and the resources it deployed to the various scenes is under way and will be published at a later date.
Following the conclusion of the two reviews, Acpo will decide whether any changes need to be made to its firearms manual or tactics.
Among the national policy changes Mr Whiting recommended was that people who receive wholly suspended sentences of jail terms of three months or more would in future be automatically classed as a prohibited person and banned from holding a guns licence for five years.
Bird would have lost his shotgun certificate in 1990 under the proposed law change but would have been able to reapply for his licence.
He said the recommendation was "very much influenced" by the Cumbria shootings.
"I cannot say it would have made a difference in this case but it would have been another significant factor to take into account," he said.
Mr Whiting recommended Acpo support the proposal which would then be passed to the Government for consideration.
He also said a key improvement would be to establish formal data links between GPs, mental health and police services to enable medical professionals to be in a position to alert police to any concerns over gun certificate holders.
A formal requirement could be put in place for doctors to be notified of an application for grant or renewal of a licence. Currently they do not hold that information unless the patient volunteers it.
He also suggested that police make a formal inquiry of family members of an applicant regarding their suitability.
Mr Mackey said he fully supported the recommendations in "trying to close and limit the opportunities for individuals who are unsuitable to get access to lawfully held firearms".
Commenting on the overall report, he said: "It is important for Cumbria Constabulary to ensure that firearms certificates are issued in line with national guidelines and legislation.
"I requested a comprehensive review following the shootings as I wanted to ensure our decision making and actions in respect of Bird's firearms certificates were appropriate.
"I wanted Derrick Bird's victims, the families of those who were killed, the local community and our police officers and staff to be confident that our firearms licensing procedures were robust and fit for purpose.
"ACC Whiting's review has confirmed that Bird owned his firearms lawfully and that we could not have used our firearms licensing process to identify him as a risk or prevent the tragic shootings in west Cumbria."
The relatives of the victims were given the opportunity to view the report before it was published today, Mr Mackey said.