The NBA won't allow players to wear "ninja-style headwear" this season.

Several players -- including the Miami Heat's Jimmy Butler, the New Orleans Pelicans' Jrue Holiday, the LA Clippers' Montrezl Harrell, the Minnesota Timberwolves' Karl-Anthony Towns and the Brooklyn Nets' Jarrett Allen -- regularly wore the headgear a season ago.

The NBA never had a formal process to approve the headgear, and allowed players to wear it during the 2018-19 season because, spokesman Mike Bass told ESPN, "We didn't want to cause a disruption by intervening midseason."

Jimmy Butler, pictured here while with the 76ers, was one of several high-profile players to wear the ninja-style headwear last season. Jesse Johnson/USA TODAY Sports

The NBA notified teams in May that the headbands wouldn't be a part of this season's approved uniforms.

The NBA's competition committee discussed the headwear as part of its meetings in Chicago on Monday. A source told ESPN that some members expressed concerns on safety, including the looseness of the headwear.

"The ninja-style headwear is not part of the NBA uniform and hasn't been through the league approval process," Bass told ESPN in a statement. "Teams have raised concerns regarding safety and consistency of size, length and how they are tied, which requires a thorough review before consideration of any rule change.

"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."