The National Collegiate Athletic Association announced a ban on composite bats in 2009 and the National Federation of State High School Associations did so in 2010.

WSJ: Little League Bans Composite Bats

Among the organizations with full or partial bans of composite bats: Little League International, Babe Ruth League, the National Federation of High School Associations, and the NCAA. In most cases, if a bat meets certain standards basically, not having any more pop than a wood or aluminum bat it will be allowed.

FORBES: Composite bat bans have sporting goods industry crying foul

Mr Ball next treats us to a brisk description of the human eye (remember rods and cones from school biology?), an explanation of why Newton was right and Goethe wrong about the composite character of white light, and an account of the 19th-century regimentation of the continuous colour spectrum by means of colour wheels and other classifying devices.

ECONOMIST: Science and history of colour