He continued his studies in the Law School of the Democritus University of Thrace, obtaining a Ph.D. in Penal and Criminal Science.

He completed his academic studies in the University of Heidelberg, Germany, with a Major of Sciences in Legal Terminology, Language and Culture.

He remained active until 2002, when he quit his position to undertake responsibilities in the coordinating committee of the plenary of presidents of the bar associations of Greece.

In 2007, Petalotis was elected on the list of the Panhellenic Socialist Movement (PASOK) to represent the Rhodope constituency in the Hellenic Parliament.

On 3 January 2015, it was announced that Petalotis would join former prime minister Papandreou in leaving PASOK to found the new Movement of Democratic Socialists.