Separate the selectors with a comma:
.footer #one .flag li .drop_down form div,
.footer #two .flag li .drop_down form div {
/* Rules */
}
From the selectors level 3 spec:
A comma-separated list of selectors represents the union of all elements selected by each of the individual selectors in the list. (A comma is U+002C.) For example, in CSS when several selectors share the same declarations, they may be grouped into a comma-separated list. White space may appear before and/or after the comma.