  We study the $\Delta I = 1/2$ rule for kaon decays and the $B_K$ parameter
for $K^0 - {\bar K}^0$ mixing in a dual 5-dimensional holographic QCD model. We
perform, in the chiral limit, computations of the relevant four-point
current-current correlators, which depend upon self-interactions among the 5D
bulk fields. Spontaneous chiral symmetry breaking ($\chi$SB) is realized
through boundary conditions on the bulk fields. Numerical results are analyzed
in comparison with QCD, chiral perturbation theory ($\chi$PT) and data, finding
reasonable agreement with the experimental values of the $g_8$ and $g_{27}$
parameters describing the $\Delta I =1/2,3/2$ decay channels.
