Justin Bieber may be an international superstar, but someone should tell him that doesn't give him license to snark about other countries' superstars. Particularly when the superstar in question is ROYALTY.

Biebs slammed Prince William for his thinning hairline. To a British magazine no less! "I mean, there are things to prevent that nowadays, like Propecia," he said to the UK mag Rollercoaster. "I don't know why he doesn't just get those things, those products. You just take Propecia and your hair grows back. Have you not got it over here?" Facepalm. Face. Palm.

Justin Bieber at David Letterman Studios, June 2012

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Because Prince William is British royalty (like, literally, literally, royalty), Biebs isn't exactly Britain's favorite pop star right now.

"The Brits are viewing Justin Bieber's diss about Prince William's challenging hair problem in the same way you view an annoying fly buzzing around you. He needs to be swatted away," said British journalist Jessica Callan. "It's like inviting someone over for dinner and they tell you how awful your carpet is. Even if you agree, how dare they say it? So the Biebs had better watch out! Wills may be thinning on top but he is one cool royal and landed himself the hottest future queen England has ever had. How can Justin and his girly hairstyle possibly compete with that?"

Ohhhhh, snap! The Biebs just got served. And it's true. Prince William may have a receding hairline, but he's got the finest future-queen in the game wearing his chain. And while we love Justin's floppy bangs, he's only 18 -- those million-dollar locks might not last forever. He might want to do some preemptive Propecia-ing himself.

Do you think Justin should have kept his mouth shut about Prince William's hair?

Photos courtesy of Fame Flynet