EXCLUSIVE

Will Smith and Jada Pinkett Smith got a visit from L.A. County Sheriff's deputies Monday, who were there to secure the property for a little lunch the Smiths are throwing for the First Lady of the U.S. of A.

Will, Jada and Salma Hayek are hosting the $2,500-a-head lunch for Michelle Obama this Thursday. That's the bargain basement price.  If people want their pic taken with Michelle Obama, the price of admission goes up to $10k a couple -- the good news, that includes lunch.

Several units from the Emergency Operations Bureau of the Sheriff's Dept. showed up to sweep the grounds ... inside and out. 

The Smiths live in Calabasas, behind a massive gate with a long, winding road that leads to the main house.  Sheriff's deputies -- along with Secret Service -- were everywhere, looking for possible security breaches.