He was appointed Researcher of Constitutional Law in Milan in 1993 and, in 1999, became Associate Professor of Public Law in the Economics Faculty of the Università degli Studi of Turin.

Since 2001 he has served as Full Professor of Constitutional Law on the Faculty of Law of the Università degli Studi of Padua.

He is an attorney admitted to practice before the Supreme Court of Cassation, and before all the principal jurisdictions.

Judge Antonini served as advisor to the Italian Government and Parliament on matters of federalism and constitutional reform, and as President of the Commissione Tecnica Paritetica per L’attuazione del Federalismo Fiscale (COPAFF).

While serving that role, he participated in drafting Enabling Law No. 42 of 2009 (Delegation to the Government in the area of economic federalism, implementing Article 119 of the Constitution) and the eight legislative decrees passed during the sixteenth legislature, as well as other legislative reforms, such as that of the 5 per Mille program.

Judge Antonini served as a tax expert for Secit, legal advisor for the Ministry of Economy and Finance, a member of ACOFF (the Alta Commissione di Studio per la Definizione dei Meccanismi Strutturali del Federalismo Fiscale), a member of the World Political Forum, advisor to the Agency for Non-profit Organizations, a member of the academic board of Confindustria, advisor for administration of the Istituto per lo Sviluppo della Formazione Professionale dei Lavoratori (ISFOL), a member of the Academic Board of IFEL (Istituto per la Finanza Locale), member of the Administrative Council of the Cassamarca Foundation, and member of various regional monitoring bodies for subsidiarity.

He serves on the academic boards of multiple law journals.

He is a member of the Italian Association of Constitutionalists.

He serves on the academic board of the Cortile dei Gentili.

Over the course of his academic career, Judge Antonini has authored and edited numerous books, as well as over one hundred articles on topics like constitutional rights and duties, the European Union, regionalism and federalism, economic federalism, the tax system, environmental law, environmental taxation, the principle of subsidiarity, constitutional reforms, simplification, the system governing public tenders, public happiness, artificial intelligence, and more.

He has participated in and organized many national and international conferences, in law and also across disciplines.

Judge Antonini has worked with many different newspapers and journals and has been invited to speak as a guest on topics touching on his areas of expertise on cultural programs on both television and radio.

He has served as a Judge on the Constitutional Court since his election by the Parliament on 26 July 2018.