Transitions from dictatorship to democracy often raise the perplexing question of whether a new government may punish actions which, although reprehensible, were considered legal under the old regime. In these instances, the desire for condign punishment of evil acts confronts the principle that forbids retroactive criminal prosecutions. After German unification, problems of this type arose in trials of East German border guards for the use of deadly force at the Berlin Wall, along with prosecutions of military and civilian officials higher in the German Democratic Republic (GDR) chain of command. In this article, the author discusses these prosecutions and analyzes the response of the German courts to the difficult problems of retroactivity that the cases raise. In its concluding section, the article suggests that these cases may evoke issues concerning the legitimacy of the GDR that were the subject of bitter debates during Germany's divided past.