Justin Bieber to Fan: Nice to Meet You, But I Just Had to Call the Cops

Justin Bieber went out of his way to greet a fan for her birthday, but still had to call in police to deal with her ... because she made a surprise visit to his house.

TMZ has learned Justin's security team called Burbank police Friday night after a girl who just turned 18 waited about 12 HOURS in her car in front of Bieber's house for a photo op.

Officers spoke to her, but because she was on a public street they couldn't do anything about it. When Justin finally came home that evening, police filled him in on the situation. JB decided to join cops when they spoke to her a second time.