  In this note, we present criteria that are equivalent to a locally compact
Hausdorff groupoid $G$ being effective. One of these conditions is that $G$
satisfies the "C*-algebraic local bisection hypothesis"; that is, that every
normaliser in the reduced twisted groupoid C*-algebra is supported on an open
bisection. The semigroup of normalisers plays a fundamental role in our proof,
as does the semigroup of normalisers in cyclic group C*-algebras.
