He served a term as Senior Adviser on Antiterrorist Policy to the Spanish Minister of Interior following the 2004 Madrid train bombings, where he was engaged in adapting national security structures to the challenges of international terrorism.

Afterward, he was appointed Director of the Program on Global Terrorism at the Real Instituto Elcano, a Spanish think tank.

Reinares is an advisor to the Center for Global Counter-Terrorism Cooperation, and he belongs to the United Nations roster of experts on terrorism prevention.

Reinares is a member of the Council on Global Terrorism established by the Atlantic Monthly Foundation and of the academic committee of the Queen Sofía Center for the Study of Violence.

He is Chairman of the European Commission expert group on violent radicalization and Academic Director of the Permanent Seminar on Terrorism Studies at Ortega y Gasset Foundation.