“The Obama administration has released a previously [top] secret 18-page policy guidance document that lays out how potential drone targets may be chosen and approved and the President’s role in the decision-making process.” Read the full story:

http://www.cnn.com/2016/08/06/politics/obama-administration-drone-policy/

For the actual, declassified document, see:

https://www.justice.gov/oip/foia-library/procedures_for_approving_direct_action_against_terrorist_targets/download

For a related policy, see:

https://www.whitehouse.gov/sites/default/files/uploads/2013.05.23_fact_sheet_on_ppg.pdf

And see especially:

https://global.oup.com/academic/product/targeted-killings-9780199646487?cc=us&lang=en&