  We calculate the transport properties of three-dimensional Weyl fermions in a
disordered environment. The resulting conductivity depends only on the Fermi
energy and the scattering rate. First we study the conductivity at the spectral
node for a fixed scattering rate and obtain a continuous transition from an
insulator at weak disorder to a metal at stronger disorder. In the
self-consistent Born approximation the scattering rate depends on the Fermi
energy. Then it is crucial that the limits of the conductivity for a vanishing
Fermi energy and a vanishing scattering rate do not commute. As a result, there
is also metallic behavior in the phase with vanishing scattering rate and only
a quantum critical point remains as an insulating state.
