The detailed circumstances in which a US government may order the killing of an American citizen who is a high-ranking member of al-Qaida have been revealed in a leaked memo prepared by Obama administration lawyers.

The document, acquired by NBC and dating from 2011, lays out for the first time the precise rationale for carrying out targeted killings of senior al-Qaida members who are US citizens, and who are believed to pose an “imminent threat of violent attack” against the United States.

Although the white paper deals specifically with the issue of when and how the president can order the killing of a US citizen who is a member of al-Qaida, it also provides one of the most comprehensive accounts of the wider international legal framework the US believes supports its controversial drones policy.

Although the paper does not specify the “minimum legal requirements” for launching such an operation, it insists that the killing would be constitutionally justified as the United States is engaged in an “armed conflict”, as defined by international law and authorised by Congress, with al-Qaida and its affiliates.

In a key passage in the document – which is unsigned – it argues that for a US citizen who has rights under the due process clause and the fourth amendment, “that individual’s citizenship would not immunize from a lethal operation”.

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