Jesse McCartney wants everyone to know ... if you publish a nude photo of him -- even one that looks like him -- he'll sue you.

The photo is floating around ... showing what looks like a naked McCartney all by his lonesome, laying on a bed with a candy G-string, fully exposed. According to the New York Post, it's being shopped around by an angry ex. Someone sent it to TMZ on Dec. 22, but we did not publish it.

McCartney's lawyer, Shawn Chapman Holley, has fired off a cease and desist letter to any web site that would dare publish the photo.

Holley warns, "a person is attempting to circulate a nude photo which purports to be Mr. McCartney." She goes on, "McCartney was unaware of the taking of this alleged photo, did not knowingly participate in the taking of this photo, and certainly did not consent to the taking of such photo."

Holley says in the letter, "it appears that this photo has been manipulated and doctored by computer software."

Holley says the publication of the photo "would be a grave invasion of Mr. McCartney's privacy rights" and she'll go after anyone who publishes it for "substantial monetary damages."

Jesse McCartney's neighbors have had it up to their eardrums with the former boy bander -- and this weekend they made the cops pay Jesse's loud ass a visit.

We're told the 21-year-old threw a huge, loud party at his Hollywood Hills pad Saturday night; the neighbors sucked it up and let it slide. But on Sunday, our sources say McCartney had the volume blasted so high on his television that his neighbors just couldn't take the racket anymore.

Cops were called to the scene, but Jesse turned his obnoxious set down and no citations were given.

Back in March, Jesse's ragers annoyed the neighborhood so much that a notice went out around the area instructing residents to call 911 if things got out of hand again.

That worked real well ...

20-year-old heartthrob Jesse McCartney debuted a new darker do at a Grammys event in Los Angeles.

Why God why?! Without his hair, he has nothing! Oh wait, he's a singer, right?

Katie and Jesse, both 20, are rumored to be engaged -- this according to "The Hills" star, Lauren Conrad.

On a bulletin posted by LC on MySpace, Katie, Jesse, Whitney, Audrina and Lauren met for dinner, "Then he got down and asked her. It was so sweet! Everyone was clapping afterwards."

After dinner, the happy bunch made their way out to club Mood to celebrate -- the same club where just last year TMZ obtained a photo of an underage Jesse McCartney drinking a Corona! That photo launched an investigation of Mood. (No one under twenty-one is allowed in Mood unless it's a sponsored event.)

TMZ contacted Jesse's rep for a comment on the engagement rumor and was told, "No, not engaged."

Maybe Lauren, best friend of Katie, was just hopeful?

It was an MTV-star-studded evening at Area last night for the launch party of "The Hills." Lauren "LC" Conrad and her onscreen gals showed up ready to mingle, and get the second season off and kickin'.

Music producer "J.R." Rotem (recently dropped by Britney) had mad love for TMZ calling the site the "classiest" of them all. Could be because we're the only ones who care!

Brody Jenner and Kim Kardashian flashed their pearly whites, followed by Brandon "Greasy Bear" Davis and all his oily glory. While NBA star Dennis Rodman seemed a bit overwhelmed by the lights/camera action, Jesse McCartney and Jack Osbourne were unfazed by the attention.

See all of last night's chilly action in today's Star Catcher.

Note to Lindsay Lohan and other underage celebs: Don't go to Mood to get your (illegal) drink on.


TMZ has learned that Mood, the Hollywood club where TMZ spotted 18-year-old Jesse McCartney in violation of drinking-age laws earlier this year, was cited for allowing two under-21-year-olds to enter the premises "without lawful business." Law enforcement sources tell us that the pair, who were not named, used fake IDs to enter the club on April 6th, whereupon undercover agents for the Department of Alcoholic Beverage Control were there and caught them.

The two people under 21 were cited for "being minors in a public place." The hearing on the alleged violation was completed last month, and the ABC is recommending a 15-day suspension of their liquor license, a decision that will be made by an administrative law judge. Mood owner David Judaken tells TMZ that he is "cooperating" with the ABC and its proceedings.

Back in February, TMZ shot video of then-19-year-old Mary-Kate Olsen and then-19 Lindsay Lohan, among others, entering Mood. As of last year, Mood had never been cited even though the City of Los Angeles had issued 207 citations in 2005. Judaken told TMZ in February, "We are diligent about ID'ing people ... Certain celebrities ultimately enter lots of clubs who are not entitled to enter."

Singer Jesse McCartney arrived at Los Angeles International Airport on Saturday and was welcomed with a big juicy kiss from girlfriend Katie Cassidy, daughter of "Partridge Family" teen idol David Cassidy.

Katie is one of the few surviving cast members of the upcoming "Dallas" movie (everyone but Katie and John Travolta left the project).

The puppy love couple was caught kissing near baggage claim. Katie rushed her loverboy as soon as he was in sight!

It was another action-packed night in Hollywood (OK- when is it not?) as Josh Levine and TMZ's cameras hit the streets to bring you what you love best- the stars!

We started the night out at The Ivy where we spotted the beautiful Cindy Crawford. The supermodel, who showed up solo, ran into a just about every camera in Hollywood as she exited the ever-so-trendy restaurant.

From there it was off to the Teen Vogue Young Hollywood Party we ran into "The OC" star Rachel Bilson, MTV's Nick Cannon, TRL host Stephen Colletti with gal pal Hayden Panettiere, teen sensation Jesse McCartney and "Hustle & Flow" star Taryn Manning.

After hours comes next and where else do you think that was? Hyde- natch. Paris Hilton showed up to her usual spot along with such celebs like "Girls Gone Wild" creator Joe Francis, "Jackass 2" star Bam Margera, "Laguna Beach" hottie Kristin Cavallari, ZZ Top rocker Billy F. Gibbons, Chris Rock (again) and TMZ's favorite vixen Elisha Cuthbert.