The N0–N4 scale

The N0–N4 scale is an ordinal coding device for the degree of legal embedding of a technology in one regulatory function. It is not a maturity index, it is never summed across layers, and a restrictive regime can score low precisely because the score measures integration rather than regulatory intensity.

Three rules follow. Scores are ordinal: the step from N1 to N2 is not assumed equal to the step from N3 to N4. Normalisation is non-linear and reversible: an incident, political change or new evidence may move a layer back toward conditional treatment. The range across the seven layers is a descriptive signal of inter-layer asymmetry, not a statistical index.

Draft law is excluded from current-law scores and shown separately as sensitivity or prospective rows.

N0Unintegrated / exceptional
No stable accommodation for the technology. Not the absence of law: inherited rules constrain or exclude it.

N1Ad hoc or conditional accommodation
Bounded lawful access — testing permits, case-by-case permissions, supervised operation. Restrictive regimes still score N1.

N2Bridge-based integration
Inherited law kept operational through deeming provisions, legal fictions, equivalence or exemption clauses, provisional authorisations.

N3Dedicated institutionalisation
Stable technology- or function-specific actors, duties, authorisations and governance mechanisms exist.

N4Routinisation / mainstream recognition
Governed as an ordinary participant in the wider system, with mature enforcement, infrastructure, risk pooling and reciprocal recognition.