  We consider the isentropic compressible Euler system in 2 space dimensions
with pressure law $p({\rho}) = {\rho}^2$ and we show the existence of classical
Riemann data, i.e. pure jump discontinuities across a line, for which there are
infinitely many admissible bounded weak solutions (bounded away from the void).
We also show that some of these Riemann data are generated by a 1-dimensional
compression wave: our theorem leads therefore to Lipschitz initial data for
which there are infinitely many global bounded admissible weak solutions.
