Currently, youth bats are undergoing a similar change with the USA Bat Standard. New youth bats approved for USA Baseball's new bat standard were released in September 2017, and the new rule goes into effect on January 1, 2018. But, this isn't the first rule change that bats have seen.
On January 1, 2012, all high school and collegiate level baseball bats had to meet the BBCOR standard. This was a new bat standard to test bats and came about for a number of reasons, but mainly safety and because of bats like the Easton Stealth. BBCOR effectively replaced the BESR Certification. JustBats.com reviews what BESR is and what it entailed.