Maybe some tar barrels on the roof, as a last-line of defense!
Have some pike-men stationed at various locations through out the lawn (move their positions each hour and each day, so as not to set a pattern)!
Whatever it takes to keep the peasants at bay!
I can here it now, a Secret Service man reports, “Sire, the peasants are revolting.” Obama, in his best Mel Brooks voice, “You said it. They stink on ice!”