We show that the local gauge group Sp(4)\ifmmode\times\else\texttimes\fi{}U(1) can be adopted to obtain the standard results for the effective lowest-order weak interaction but with a $\ensuremath{\Delta}I=\frac{1}{2}$ nonleptonic current-current interaction. Some other features of our model are the presence of heavy leptons, the cancellation of triangle anomalies between leptons and quarks if the latter carry charm and color, and, at least in one version, the presence of two extra quarks with the same charge as $u$ and $c$.