Tilley received her BA in Political Science from Antioch College (1986) and an MA from the Centre for Contemporary Arab Studies at Georgetown (1988).
[citation needed] After finishing her MA in Arab Studies at Georgetown, she served as Assistant Director of the International Organisation for the Elimination of All Forms of Racial Discrimination (EAFORD) in Washington DC, where she developed a second field in the politics of indigenous peoples.
She was appointed as Associate Professor in 2003[6] but in 2005 took leave to conduct research in South Africa, initially at the Centre for Policy Studies in Johannesburg.
[10] In her second book, she edited a co-authored study, commissioned by the South African Government and conducted at the HSRC, which found that Israeli policies in the West Bank and Gaza Strip are consistent with colonialism and apartheid as these regimes are codified in international law.
Released initially in 2009, this study was later published in 2012 by Pluto Press under the title Beyond Occupation: Apartheid, Colonialism and International Law in the Occupied Palestinian Territories.
Her book on Salvadoran indigenous identity, titled Seeing Indians: A Study of Race, Nation and Power in El Salvador, was published by the University of New Mexico Press in 2005.
"[15] UN Secretary-General António Guterres distanced himself from the report, which he stated had been released without authorization, and ordered its removal from the ESCWA website.