  The metal-insulator crossover of the in-plane resistivity upon temperature
decrease, recently observed in several classes of cuprate superconductors, when
a strong magnetic field suppresses the superconductivity, is explained using
the $U(1)\times SU(2)$ Chern-Simons gauge field theory. The origin of this
crossover is the same as that for a similar phenomenon observed in heavily
underdoped cuprates without magnetic field. It is due to the interplay between
the diffusive motion of the charge carriers and the ``peculiar'' localization
effect due to short-range antiferromagnetic order. We also calculate the
in-plane transverse magnetoresistance which is in a fairly good agreement with
available experimental data.
