  Within the spirit of Dirac's canonical quantization, noncommutative spacetime
field theories are introduced by making use of the reparametrization invariance
of the action and of an arbitrary non-canonical symplectic structure. This
construction implies that the constraints need to be deformed, resulting in an
automatic Drinfeld twisting of the generators of the symmetries associated with
the reparametrized theory. We illustrate our procedure for the case of a scalar
field in 1+1- spacetime dimensions, but it can be readily generalized to
arbitrary dimensions and arbitrary types of fields.
