Ivar was a pen name used by Robert Silverberg. The ship here is landing, not leaving. This reviewer says:

It’s the story of Johnny Mantell, a beachcomber and bum on the resort planet Mulciber, who has to flee from his peaceful existence because he’s unjustly accused of murder. He steals a spaceship and heads for Starhaven, a giant metal-enclosed sanctuary world where criminals of all sorts, even murderers, can find, well, haven. Naturally enough, on a world populated by criminals there aren’t any laws, so Johnny may have his work cut out just surviving on Starhaven.

It's one thing to imagine an island or a town that's mostly given over to criminality, but an entire planet? With metal enclosing the entire thing like a small Dyson sphere? Who'd pay for the maintenance?