In 1909, Petrosino made plans to travel to Palermo, Sicily on a secret mission. A recently passed federal law allowed the U.S. government to deport any alien who had lived in the country for less than three years if that alien had been convicted of a crime in another country. Petrosino was armed with a long list of known Italian criminals who had taken up residence in the United States, and intended to get enough evidence of their criminal pasts to throw them out of the country once and for all. However, there were already signs that the secrecy and success of the mission was in jeopardy: A few weeks before his departure, New York newspaper articles cited anonymous sources hinting at the purpose of Petrosino's covert mission and the US Ambassador to Italy, Lloyd Carpenter Griscom, expressed concerns directly to Petrosino that he would be recognized in Sicily by "perhaps a thousand criminals". Subsequently, while in Rome, Petrosino became aware that he was being followed—and told a friend that the man following him, whom he recognized from New York and later observed ducking into a telegraph office, had likely alerted his Black Hand Society compatriots in Noto, Sicily that he (Petrosino) was now in Italy.