García-García *et al.*[@Garcia-Garcia05] proposed that such Onsager constraints carry over directly to electrostatic polarizabilities. Here we rigorously derive Onsager relations for electrodynamic magneto-electric point scatterers. By, definition, the electric and magnetic fields due to the induced $\bm{p}$ and $\bm{m}$ are equal to $$\left(
\begin{array}{c}
\bm{E}_{\mathrm{out}}\\
\bm{H}_{\mathrm{out}}
\end{array}\right)
=\boldsymbol{G}^0(\bm{r},\bm{r}')\left(
\begin{array}{c}
\bm{p}\\
\bm{m}
\end{array}\right),
\label{Eq:dipoleG}$$ with a dyadic Green tensor $\boldsymbol{G}^0$ that describes the field at position $\bm{r}=(x,y,z)$ due to a dipole at $\bm{r'}=(x',y',z')$. The 6$\times$6 Green dyadic of free space can be divided in four 3$\times$3 blocks $$\boldsymbol{G}^0(\bm{r},\bm{r}') =\left(
\begin{array} {c c}
\boldsymbol{G}^0_{EE}(\bm{r},\bm{r}') & \boldsymbol{G}^0_{EH}(\bm{r},\bm{r}')\\
\boldsymbol{G}^0_{HE}(\bm{r},\bm{r}') & \boldsymbol{G}^0_{HH}(\bm{r},\bm{r}')
\end{array} \right)
\label{Eq:freeG}$$ The 3$\times$3 diagonals correspond to the familiar known electric field Green dyadic [@Pedro98; @Abajo07] and magnetic field Green dyadic of free space, which in our unit system (see Appendix) both equal $$\boldsymbol{G}^0_{EE}(\bm{r},\bm{r}')=\boldsymbol{G}^0_{HH}(\bm{r},\bm{r}')=
(\mathbb{I}k^2+\nabla\nabla)
 \frac{e^{ik|\bm{r}-\bm{r'}|}}{|{\bm{r}-\bm{r'}}|}.
\label{Eq:freeGEE}$$ The off diagonal blocks correspond to the mixed dyadics that specify the electric field at $\bm{r}$ due to a magnetic dipole at $\bm{r'}$, respectively the magnetic field at $\bm{r}$ due to an electric dipole at $\bm{r'}$. Explicitly: $$\begin{aligned}
\boldsymbol{G}^0_{EH}(\bm{r},\bm{r}') & =&
-\boldsymbol{G}^0_{HE}(\bm{r},\bm{r}') \nonumber \\ & =& ik \left(
\begin{array} {c c c}
0 & \partial_z & -\partial_y\\
-\partial_z & 0 & \partial_x\\
\partial_y & -\partial_x 