The Referee can give a Yellow Card for behavior which in the Referee's judgment is unsporting or causes an unfair advantage. Examples which are mentioned in the rules, "Questions and Answers", the soccer official’s guidebook and other sources we’ve been able to find include: any action designed to deceive the Referee; behavior which in the Referee's judgment is unsporting or causes an unfair advantage; faking an injury; saying things that are designed to confuse or distract an opponent ...
– U.S. Soccer has come up with the term “FEDDD-UP” to remember the seven yellow card offenses for field players: Fails to respect required distance; Enters the field without permission; Deliberately leaves without permission; Dissent by word or action; Delays the restart of play; Unsporting Behavior; Persistent infringement of the Laws.
Before he can roll the ball into the net, you blow the whistle for unsporting behavior, caution the striker, and award an indirect free kick.
Unsporting behavior Showing dissent by word or action Persistently infringes on the Laws of the Game Delays the restart of play Failure to respect the required distance when play is restarted with a corner kick or free kick Enters or re-enters the field of play without the referee's permission
is guilty of unsporting behavior; shows dissent by word or action; persistently infringes the Laws of the Game; delays the restart of play; fails to respect the required distance when play is restarted with a corner kick or free kick; enters or re-enters the field of play without The Referee's permission
That purpose is to enable the referee to apply common sense and intelligence in enforcing the Laws of the Game. Unsporting behavior is any act that could bring the game into disrepute, i. e., any act that runs counter to the spirit of fair play.
Misconduct Restarts. When the ball is in play and a player commits an offense outside the field of play: if the player is already off the field –restart is a dropped ball. if the player leaves the field to commit the offense - restart is an IFK from the position of the ball when play was stopped.
If a player slide tackles from the front, it will be considered at least "dangerous play" (which is an indirect kick foul), or kicking, or tripping, or "unsporting behavior", even if the ball is contacted, since it would at the least be reckless or dangerous. (See "Cards, Red Card, Serious Foul Play")