 Why was it unheard of to issue an effective prison sentence to the zarquil operators?
Zarquil was extremely illegal, of course—so much so that there were many legitimate citizens who weren't quite sure just what the word implied, knowing merely that it was one of those nameless horrors so deliciously hinted at by the fax sheets under the generic term of "crimes against nature." Actually the phrase was more appropriate to zarquil than to most of the other activities to which it was commonly applied. When the zarquil operators were apprehended, which was not frequent—as they had strange powers, which, not being definable, were beyond the law—they suffered their sentences with equanimity. No Earth court could give an effective prison sentence to a creature whose life spanned approximately two thousand terrestrial years.
 The operators lived significantly long lives
 The operators were above the law  The operators were too difficult to contain in a prison  The operators lived significantly long lives  The laws were difficult to enforce and harder to uphold