This paper revisits Julio H. G. Olivera’s largely forgotten theory of monetary heteronomy, developed between 1977 and 1983. In modern terms, Olivera reduces Mundell’s trilemma to a dilemma: under passive international money, only the monetary leader can simultaneously control its domestic money supply and the international value of its currency; other countries must choose between the two. Floating therefore does not necessarily restore monetary autonomy. Evidence from trilemma indexes and high-frequency monetary-policy shocks shows that floating provides only partial monetary autonomy and that international monetary influence remains hierarchical. The results challenge the conventional view that floating exchange rates automatically establish monetary autonomy.