For quite a few years, the Snell Foundation was criticized for having a test standard that encouraged too hard of lining, as the tests required all size helmets to use the same identical 5 kg mass headform, and to withstand multiple blows to the exact same location.
One of the motorcycle magazines attacked Snell strongly for this with their own independent test, and a comparison to Euro standards which had a much softer lining. The magazine editor was canned for losing all that helmet advertising business, but it may have save a few people's lives.
Snell finally admitted the error of their ways, and the SA2010 / M2010 standards used a graduated headform mass from the smallest to largest size helmet.
Now Snell has added a few more test features for SA2015:
http://www.smf.org/standards/sa/2015/SA2015releaseNotes.pdf
Some manufacturers have also introduced a liner for 2015 that has internal corrugations like a small egg crating pattern that should absorb energy more gradually. I am guessing this is in response to the new low speed test criteria.
So, I would encourage everyone to purchase the newest Snell standard, or find an ECE standard helmet, and try to convince the tech inspector that Snell is not the only standard in the world.