We consider a few individuals whose task is to confine a moving population. This is a control problem where the state to be controlled is a compact subset of R-n. We first prove a negative result on the impossibility of confinement, a key assumption being a sufficiently large initial volume. Then a positive result is also provided through the construction of a confining control, when the initial set has a suitable diameter. Numerical integrations show possible behaviors when the above results do not apply.