  We constrain the light CP-odd Higgs $A_{1}^{0}$ in NMSSM via the rare decay
$\pi^{0}\to e^{+}e^{-}$. It is shown that the possible $3\sigma$ discrepancy
between theoretical predictions and the recent KTeV measurement of ${\cal
B}({\pi}^{0}\to e^+ e^-)$ cannot be resolved when the constraints from
$\Upsilon\to\gamma A_1^0$, $a_{\mu}$ and $\pi^{0}\to \gamma \gamma$ are
combined. Furthermore, the combined constraints also exclude the scenario
involving $m_{A_1^0}=214.3$ MeV, which is invoked to explain the anomaly in the
$\Sigma^{+}\to p \mu^{+}\mu^{-}$ decay found by the HyperCP Collaboration.
