  GRB 230307A is the second brightest gamma-ray burst (GRB) ever detected over
50 years of observations and has a long duration in the prompt emission. Two
galaxies are found to be close to the position of GRB 230307A: 1) a distant ($z
\sim 3.87$) star-forming galaxy, located at an offset of $\sim
0.2\operatorname{-}0.3$ arcsec from the GRB position (with a projected distance
of $\sim 1\operatorname{-}2 \, \rm kpc$); 2) a nearby ($z= 0.065$) spiral
galaxy, located at an offset of 30 arcsec (with a projected distance of $\sim
40 \, \rm kpc$). Though it has been found that the brightest GRBs are readily
detected in GeV emission by the Fermi Large Area Telescope (LAT), we find no
GeV afterglow emission from GRB 230307A. Combining this with the optical and
X-ray afterglow data, we find that a circum-burst density as low as $\sim
10^{-5} \operatorname{-} 10^{-4}~{\rm cm^{-3}}$ is needed to explain the
non-detection of GeV emission and the multi-wavelength afterglow data,
regardless of the redshift of this GRB. Such a low-density disfavors the
association of GRB 230307A with the high-redshift star-forming galaxy, since
the proximity of the GRB position to this galaxy would imply a higher-density
environment. Instead, the low-density medium is consistent with the
circumgalactic medium, which agrees with the large offset between GRB 230307A
and the low-redshift galaxy. This points to the compact stellar merger origin
for GRB 230307A, consistent with the detection of an associated kilonova.
