Due to safety concerns related and issues regarding consistency in length and size, the NBA has banned the "ninja-style headwear" that became popular among players last season.
League spokesperson Mike Bass told Adrian Wojnarowski of ESPN.com that the headbands that players manually tie around their head had not gone through the league approval process.
"When some players began wearing them last season, we didn't want to cause a disruption by intervening midseason, but we notified our teams in May that they would not be part of this season's uniforms," Bass told Wojnarowski.