Face guarding in basketball is defined as the act of blocking or disrupting the vision of an offensive player regardless of whether he actually has the basketball. It has been illegal at all levels of basketball since 1913 and is listed in the rule book as an "Unsportsmanlike Act." Face guarding is explicitly mentioned in the high school rule book, the NCAA rule book and the International rule book with the penalty being a technical foul.
High School Basketball
The rules for most high school athletic programs in the United States are overseen by a governing body known as the National Federation of State High School Associations, or the NFHS. In 1913 the NFHS first mentioned face guarding in its rule book, stating that it was illegal for a defensive player to deliberately block the vision of an offensive player. Although it was first instated in 1913, there was no further ruling until 2004 when the NFHS made it a point of emphasis. At that time, a memo was sent to officials nationwide stating that the rule was to include actions occurring away from the ball as well as for players guarding the ball.
The major governing body of college basketball, the National Collegiate Athletics Association, asserts in Rule 10, Section 6, Article 1 of its rule book that purposefully obstructing an opponent's vision by waving or placing hands near her eyes should result in a technical foul. The technical foul will result in free throws for the opposing team, and they will be rewarded with possession of the ball.
Much like high school and college basketball, the governing body for international ball, FIBA, states in its rules that "baiting an opponent or obstructing his vision by waving his hands near the eyes" is a technical foul and should result in the opposing team shooting free throws and gaining possession of the basketball.
Unlike other levels of basketball, face guarding in the National Basketball Association is a grey area. Although the rule book mentions something about eye guarding, eye guarding is different than face guarding. While there is no technical foul called for face guarding in the NBA, typically if contact is made with the head of an opposing player, a personal foul is called.