  We point out that, given the current experimental status of radiative kaon
decays, a subclass of the ${\cal O} (p^4)$ counterterms of the weak chiral
lagrangian can be determined in closed form. This involves in a decisive way
the decay $K^\pm \to \pi ^\pm \pi ^0 l^+ l^-$, currently being measured at CERN
by the NA48/2 and NA62 collaborations. We show that consistency with other
radiative kaon decay measurements leads to a rather clean prediction for the
${\cal{O}}(p^4)$ weak couplings entering this decay mode. This results in a
characteristic pattern for the interference Dalitz plot, susceptible to be
tested already with the limited statistics available at NA48/2. We also provide
the first analysis of $K_S\to \pi^+\pi^-\gamma^*$, which will be measured by
LHCb and will help reduce (together with the related $K_L$ decay) the
experimental uncertainty on the radiative weak chiral couplings. A precise
experimental determination of the ${\cal{O}}(p^4)$ weak couplings is important
in order to assess the validity of the existing theoretical models in a
conclusive way. We briefly comment on the current theoretical situation and
discuss the merits of the different theoretical approaches.
