First, I want to thank Ken Butcher for sending me various files in electronic format concerning the NIST Training Course for Officials who have the duty of verifying the net amounts inside packages intended for consumers in retail markets.
My conclusion is that Metric-Only Enforcement of labeling declarations is completely compliant with requirements of both the current FPLA, and the current UPLR (as defined in the 2014 Editions of NIST Handbooks 130 and 133). Although "duality" of units of measurement (units from the SI and units from outside the SI) continues to be required on the labels of consumer commodities by the current FPLA, there is absolutely no exclusion of metric-only verification of net amounts inside packages by the current FPLA. The only limitation is that net amounts not be overstated, after rounding to three significant digits, by the part of the label stated in units from outside the SI. My hope is that the new revised FTC rules will be consistent with this interpretation. Eugene Mechtly
