ANAB Accreditation Rule 20 references the ANAB Management Systems Accreditation Manual, which defines major and minor nonconformities as follows for CBs. Note that these definitions are applicable to CBs and not ISO 9001-registered organizations, so this does not appear to be what was requested.
ANAB definitions:
Major nonconformity: Absence of or failure to implement and maintain one or more requirements for accreditation or requirements of the CB’s certification system or the CB’s management system, which would on the basis of available objective evidence raise significant doubt as to the credibility of the certificates issued by the CB; or a number of minor nonconformities to one or more requirements, which when combined represent a breakdown of the CB’s systems; or a minor nonconformity previously issued and not addressed effectively.
Minor nonconformity: Observed lapse in the CB’s systems that does not represent a breakdown of the CB’s systems and does not raise significant doubt with regard to the credibility of any certificates issued by the CB.
CBs appear to define major and minor themselves, and I could not find a publicly-available definition from most of the CBs that I checked. However, SRI does have the below definitions and "should" statement in their QP 5.0 On-Site Audit Procedure:
1.4.3 Major (Hold) Nonconformity: any or all of the following:
A. A nonconformity that impacts the capability of the management system to achieve the intended results.
B. The absence of or total breakdown of a system to meet a management system requirement. A number of minor nonconformities against one requirement can represent a total breakdown of the system.
C. Any noncompliance that would result in the probable shipment of nonconforming product. A condition that may result in the failure or materially reduce the usability of the products or services for their intended purpose.
D. A noncompliance that judgement and experience indicate is likely either to result in the failure of the management system or to materially reduce its ability to assure controlled processes and products.
E. There is significant doubt as to the capability of the management system to achieve the policy and objectives of the organization.
1.4.4 Minor Nonconformity: A nonconformity that DOES NOT impact the capability of the management system to achieve the intended results. Nonsystemic nonconformance that does not fall clearly into a Major nonconformity category and has minimal impact and significance on the system.
2.5.8 ...
Nonconformities should be classified into Hold (major) or Minor. ...
I haven't found any requirement for CBs to make a major/minor differentiation, but they seem to be allowed to do it by ISO 17021 and choose to do so (maybe because they find it helpful for their processing and because it is the norm).
If the CB writes major and minor definitions (and requirements for auditors to classify nonconformances as such) in their procedures, then that is the mandate for the auditor to identify a nonconformance as major or minor.
It appears that the only specific 'requirement' is established by the CB (e.g. DQS, IAF, BSI, etc..etc..etc..etc..)
I think this is correct.
ANAB Accreditation Rule 20
ANAB Management Systems Accreditation Manual
SRI Procedures