Presumably it depends on the total mAh of the battery shipment.
mAh is the milliamphours.
It is a measure of the energy stored in the battery.
The link ENAUD posted mentioned 30% max charge on international(as I recall) and
capacity was mentioned as a factor.
After reading that(and judging from the actual transcript of 2012 law) it appears capacity, according the law, is based on watts-hours. I don't know why they decided to use this standard when the battery industry has clearly established mah.
The two are mathematically interchangeable via ohms law, but our beloved
mod batteries are labeled as mah. It's not likely your average mail clerk has even seen an Ohm's wheel diagram; let alone understand how to use one.
If I didn't know better I'd think they intentionally complicated this law for future clarification. Legislative 'busy work' and meddling. Or have I just misinterpreted?