  It is proved that dynamically formed Reissner-Nordstr\"om-de Sitter (RNdS)
black holes, which have recently been claimed to provide counter-examples to
the Penrose strong cosmic censorship conjecture, are characterized by unstable
(singular) inner Cauchy horizons. The proof is based on analytical techniques
which explicitly reveal the fact that {\it charged} massive scalar fields in
the charged RNdS black-hole spacetime are characterized, in the large-coupling
regime, by quasinormal resonant frequencies with
$\Im\omega^{\text{min}}<{1\over2}\kappa_+$, where $\kappa_+$ is the surface
gravity of the black-hole event horizon. This result implies that the
corresponding relaxation rate $\psi\sim e^{-\Im\omega^{\text{min}}t}$ of the
collapsed charged fields is slow enough to guarantee, through the
mass-inflation mechanism, the instability of the dynamically formed inner
Cauchy horizons. Our results reveal the physically important fact that, taking
into account the unavoidable presence of {\it charged} matter fields in
dynamically formed {\it charged} spacetimes, non-asymptotically flat RNdS black
holes are globally hyperbolic and therefore respect the fundamental strong
cosmic censorship conjecture.
