... or else you're grounded!

Lindsay Lohan's in big trouble. While all the adults in her life are busy fawning over her and raking in the dough while she self-destructs, one particular grown-up has decided he doesn't want to put up with her shit.

It's about time someone acts like the parent around this girl! Now she might live to see 21 and actually be legal to club-hop and get loaded.

The head of the production company of her current film has put her in her place and warned her that he's not impressed. Here's the letter he wrote.

It's gonna be hard to sneak cocaine on the set now that she's being watched.