"This would give us assurance that online purchasing regimes would have necessary protections, but politicians rejected registration."
However, the Police Association's own policy went further and wanted the online sales of firearms banned.
The Police Association said the existing firearms regulations fell short as it did not ensure all people buying firearms had licences or that those purchased actually went to the licenced person who purchased the weapon online.
Cahill said significant improvements would need to be made to ensure only clearly identifiable licensed firearms owners could purchase and receive firearms before the association relaxed its position.
The Police Association said Trade Me supported its view that there should be a register of all firearms serial numbers.