  We investigate one of the consequences of the twisted Poincare symmetry. We
derive the charge conservation law and show that the equivalence principle is
satisfied in the canonical noncommutative spacetime. We applied the twisted
Poincare symmetry to the Weinberg's analysis. To this end, we generalize our
earlier construction of the twisted S matrix \cite{Bu}, which apply the
noncommutativity to the fourier modes, to the massless fields of integer spins.
The transformation formula for the twisted S matrix for the massless fields of
integer spin has been obtained. For massless fields of spin 1, we obtain the
conservation of charge, and the universality of coupling constant for massless
fields of spin 2, which can be interpreted as the equality of gravitational
mass and inertial mass, i.e., the equivalence principle.
