  We have observed the large Bok globule CB 54 in 850$\mu$m polarised light
using the POL-2 polarimeter on the James Clerk Maxwell Telescope (JCMT). We
find that the magnetic field in the periphery of the globule shows significant,
ordered deviation from the mean field direction in the globule centre. This
deviation appears to correspond with the extended but relatively weak $^{12}$CO
outflow emanating from the Class 0 sources at the centre of the globule.
Energetics analysis suggests that if the outflow is reshaping the magnetic
field in the globule's periphery, then we can place an upper limit of
$<27\,\mu$G on the magnetic field strength in the globule's periphery.
Comparison with archival Planck and CARMA measurements shows that the field in
the centre of the globule is consistent over several orders of magnitude in
size scale, and oriented parallel to the density structure in the region in
projection. We thus hypothesise that while non-thermal motions in the region
may be sub-Alfv\'enic, the magnetic field is subdominant to gravity over a wide
range of size scales. Our results suggest that even a relatively weak outflow
may be able to significantly reshape magnetic fields in star-forming regions on
scales $> 0.1$ pc.
