The unglossed headword is nominative plural of the noun leiponau/ths. It appears in the accusative plural in the quotation given. The word is otherwise unattested in this leip- form.
Pollux 8.40, 42-43 suggests that this offense was prosecuted in Athens by a graphe l(e)iponautiou. See further Hamel (art.cit. below).
[1] The quotation is unidentifiable, so it is not clear what event is being referred to, or who 'they' are. The subject-matter is reminiscent, however, of the decree allegedly passed by the Athenians prior to the battle of Aigospotamoi (405 BCE). See Xenophon, Hellenica 2.1.31: the Athenians resolved to cut off the right hands of all those they captured if they won the battle. See also Plutarch, Lysander 9.5; Aelian, Varia Historia 2.9; Cicero, De Officiis 3.11.46. For discussion see Debra Hamel, Athenian Generals: Military Authority in the Classical Period (Leiden 1998) 51.