Michelle Obama's Jeweler -- Gastineau Girls Are Ripping Off My Smithsonian Style!!!

Lisa and Brittny Gastineau aren't just a couple off small-time jewelry thieves ... they're ripping off one of the most famous jewelers in American history -- so says the famous jeweler herself.

Loree Rodkin -- who has designed jewelry for Michelle Obama, Cher, Madonna, Sting, Steven Tyler, Elton John, and others -- is suing Lisa Gastineau and her daughter over their new jewelry line Tres Glam ... claiming their designs are Tres Stolen.

Loree claims she's so famous ... her Michelle Obama ring and jewelry designs from the 2009 inaugural ball are part of the permanent collection of the Smithsonian National Museum of American History.

Loree claims Tres Glam has been shamelessly ripping off SEVERAL of her recent designs -- which are copyrighted -- including the below "Spider Web Bondage Ring" ... and she's demanding the Gastineaus put an end to it ASAP.

Loree is suing for at least $150,000 per alleged copyright infringement ... and she's demanding they stop selling the products asap.

Calls to the Gastineaus weren't returned.