Iran accelerates plans to unify its two-tier exchange rate system in a desperate attempt to stabilize its plummeting currency amid geopolitical uncertainty. But efforts to impose currency controls look unenforceable and risk fomenting further dissent.

Iran on 9 April announced the unification of its official and free market exchange rates for the rial in a surprise, desperate attempt to halt the free-fall in the value of its currency. This has now plummeted to an all-time low of around...