In 2017, the group leaders League (publisher of the magazine makers) published a new ranking dedicated to the best law firms specialized in State aid. Working tool for senior executives (legal directors, CFOs, CEOs, HR managers, investment funds and other investment bankers), the ranking is done under investigation by several months. To this end, investigators League Leaders group had contact with professionals of economic law the most famous. Questionnaires were sent by the hundreds. Our rankings are based on several criteria. Among them retain the reputation of the firm, the expertise of partners and their ability to impose on files. The turnover of the studied departments as well as the growth and dynamism of the teams are also criteria that may impact on the place of the team in the rankings. Other industry professionals (auditors, institutions ...) are also asked to comment on the positioning of firms in our rankings.