  We study for subgroups $G\subseteq U(N)$ partial summations of the
$\theta$-expanded perturbation theory. On diagrammatic level a summation
procedure is established, which in the U(N) case delivers the full star-product
induced rules. Thereby we uncover a cancellation mechanism between certain
diagrams, which is crucial in the U(N) case, but set out of work for $G\subset
U(N)$. In addition, an explicit proof is given that for $G\subset U(N), G\neq
U(M), M<N$ there is no partial summation of the $\theta $-expanded rules
resulting in new Feynman rules using the U(N) star-product vertices and besides
suitable modified propagators at most a $finite$ number of additional building
blocks. Finally, we show that certain SO(N) Feynman rules conjectured in the
literature cannot be derived from the enveloping algebra approach.
