As a lawyer, Liebknecht often defended other left-wing socialists who were tried for offences such as smuggling socialist propaganda into Russia, a task in which he was also involved.
Kao odvjetnik, Liebknecht je često branio druge ljevičarske socijaliste koji su bili na sudu zbog prijestupa poput krijumčarenja socijalističke propagande u Rusiju, u što je i sam bio umiješan.