  We examine the unitarity of a class of generalized Maxwell U(1) gauge
theories in (2+1) D containing the pseudodifferential operator
$\Box^{1-\alpha}$, for $\alpha \in [0,1)$. We show that only Quantum
Electrodynamics (QED$_3$) and its generalization known as Pseudo Quantum
Electrodynamics (PQED), for which $\alpha =0$ and $\alpha = 1/2$, respectively,
satisfy unitarity. The latter plays an important role in the description of the
electromagnetic interactions of charged particles confined to a plane, such as
in graphene or in hetero-junctions displaying the quantum Hall effect.
