  Far-ultraviolet spectra obtained with $FUSE$ show that the strong
$CII\lambda$1036 interstellar absorption-line is essentially black in five of
the UV-brightest local starburst galaxies. Since the opacity of the neutral ISM
below the Lyman-edge will be significantly larger than in the $CII$ line, these
data provide strong constraints on the escape of ionizing radiation from these
starbursts. Interpreted as a a uniform absorbing slab, the implied optical
depth at the Lyman edge is huge ($\tau_0 \geq 10^2$). Alternatively, the areal
covering factor of opaque material is typically $\geq$ 94%. Thus, the fraction
of ionizing stellar photons that escape the ISM of each galaxy is small: our
conservative estimates typically yield $f_{esc} \leq 6%$. Inclusion of
extinction due to dust will further decrease $f_{esc}$. An analogous analysis
of the rest-UV spectrum of the star-forming galaxy $MS 1512-CB58$ at $z$ =2.7
leads to similar constraints on $f_{esc}$. These new results agree with the
constraints provided by direct observations below the Lyman edge in a few other
local starbursts. However, they differ from the recently reported properties of
star-forming galaxies at $z \geq$ 3. We assess the idea that the strong
galactic winds seen in many powerful starbursts clear channels through their
neutral ISM. We show empirically that such outflows may be a necessary - but
not sufficient - part of the process for creating a relatively porous ISM. We
note that observations will soon document the cosmic evolution in the
contribution of star-forming galaxies to the metagalactic ionizing background,
with important implications for the evolution of the IGM.
