${\mathit{K}}_{\mathit{L}}$→${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$

We calculate all of the form factors for the one-photon, ${\mathit{K}}_{\mathit{L}}$→${\mathrm{\pi }}^{+}$ ${\mathrm{\pi }}^{\mathrm{-}}$ ${\gamma }^{\mathrm{*}}$→${\mathrm{\pi }}^{+}$ ${\mathrm{\pi }}^{\mathrm{-}}$ ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$ contribution to the ${\mathit{K}}_{\mathit{L}}$→${\mathrm{\pi }}^{+}$ ${\mathrm{\pi }}^{\mathrm{-}}$ ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$ decay amplitude at leading order in chiral perturbation theory. These form factors depend on one unknown constant that is a linear combination of coefficients of local O(${\mathit{p}}^4$) operators in the chiral Lagrangian for weak radiative kaon decay. We determine the differential rate for ${\mathit{K}}_{\mathit{L}}$→${\mathrm{\pi }}^{+}$ ${\mathrm{\pi }}^{\mathrm{-}}$ ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$ and also the magnitude of two CP-violating observables.