  It is argued on the basis of the BCS theory that the zero-$T$ penetration
depth satisfies $ \lambda^{-2}(0)\propto\sigma T_c $ ($\sigma$ is the normal
state dc conductivity) not only in the extreme dirty limit $\xi_0/\ell \gg 1$,
but in a broad range of scattering parameters down to $\xi_0/\ell \sim 1$
($\xi_0$ is the zero-$T$ BCS coherence length and $\ell$ is the mean-free
path). Hence, the scaling $ \lambda^{-2}(0)\propto\sigma T_c $, suggested as a
new universal property of superconductors,\cite{Homes} finds a natural
explanation within the BCS theory.
