The Fair Packaging and Labeling Act is a US law that applies to labels on many consumer products. It requires the label to state:

the identity of the product; the name and place of business of the manufacturer, packer, or distributor; and the net quantity of contents.

The contents statement must include both metric and inch/pound units.

Passed under Lyndon Johnson in 1966.

FPLA in full (http://lamar.colostate.edu/~hillger/laws/fpla-cfr.html)