Professional sports are the games in which there is a payment for the participants. NBA players cannot sign autographs using a blue marker is not an actual rule in professional sports.
Professional sports include the leagues and matches of cricket, football, volleyball, basketball, etc. The NBA, PGA, NFL, and MLB are some of the professional leagues and sports associations.
In NBA, it is not a rule that a player cannot give an autograph using a blue marker. In PGA, players can wear denim, and in MLB, players cannot catch a baseball in their hats.
Therefore, an NBA player cannot sign with a blue marker is not a rule.
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