  The Casimir force between a pair of parallell plates filled with ionic
particles is considered. We use a statistical mechanical approach and consider
the classical high temperature limit. In this limit the ideal metal result with
no transverse electric (TE) zero frequency mode is recovered. This result has
also been obtained by Jancovici and \v{S}amaj earlier. Our derivation differs
mainly from the latter in the way the Casimir force is evaluated from the
correlation function. By our approach the result is easily extended to
electrolytes more generally. Also we show that when the plates are at contact
the Casimir force is in accordance with the bulk pressure as follows from the
virial theorem of classical statistical mechanics.
