  It is well-known that the space group selection rule constrains the
interactions of closed strings on orbifolds. For some examples, this rule has
been described by an effective Abelian symmetry that combines with a
permutation symmetry to a non-Abelian flavor symmetry like $D_4$ or
$\Delta(54)$. However, the general case of the effective Abelian symmetries was
not yet fully understood. In this work, we formalize the computation of the
Abelian symmetry that results from the space group selection rule by imposing
two conditions only: (i) well-defined discrete charges and (ii) their
conservation. The resulting symmetry, which we call the space group flavor
symmetry $D_S$, is uniquely specified by the Abelianization of the space group.
For all Abelian orbifolds with $N=1$ supersymmetry we compute $D_S$ and
identify new cases, for example, where $D_S$ contains a $Z_2$ dark
matter-parity with charges 0 and 1 for massless and massive strings,
respectively.
