The constraint hypersurfaces defining the Witten and Ashtekar formulat
ions for 2+1 gravity are very different. In particular the constraint
hypersurface in the Ashtekar case is not a manifold but consists of se
veral sectors that intersect each other in a complicated way. The issu
e of how to define a consistent dynamics in such a situation is then r
ather non-trivial. We discuss this point by working out the details in
a simplified (finite-dimensional) homogeneous reduction of 2+1 gravit
y in the Ashtekar formulation.