[rodonn]

The Clayton act explicitly includes partial acquisition as still being covered. "No person engaged in commerce or in any activity affecting commerce shall acquire, directly or indirectly, the whole or any part of the stock... [where] the effect of such acquisition may be substantially to lessen competition, or to tend to create a monopoly."

There may be some other regulations that are avoided by a partial acquisition, but it doesn't bring it wholly outside of the relevant antitrust laws.