  We discuss restrictions on operators in the soft-collinear effective theory
(SCET) which follow from the ambiguity in the decomposition of collinear
momenta and the freedom in the choice of light-like basis vectors $n$ and $\bar
n$. Invariance of SCET under small changes in $n$ and/or $\bar n$ implies a
symmetry of the effective theory that constrains the form of allowed operators
with collinear fields. The restrictions occur at a given order in the power
counting as well as between different orders. As an example, we present the
complete set of higher order operators that are related to the collinear quark
kinetic term.
