Non-recognition is the practice and legal obligation not to extend diplomatic recognition to annexations or de facto states created through violation of international law. It is a counterpart to the rejection of right of conquest in modern international law and the jus cogens norm of prohibition on the acquisition of territory through force.
References
Talmon, Stefan (2006). "The Duty Not to 'Recognize as Lawful' a Situation Created by the Illegal Use of Force or Other Serious Breaches of a Jus Cogens Obligation: an Obligation without Real Substance?". The Fundamental Rules of the International Legal Order: "jus Cogens" and Obligations "erga Omnes" : [Berlin Workshop]. BRILL. pp. 99–125. ISBN 978-90-04-14981-6. 978-90-04-14981-6 ↩
Azarova, Valentina (2018). "The secret life of non-recognition: EU-Israel relations and the obligation of non-recognition in international law". Global Affairs. 4 (1): 23–37. doi:10.1080/23340460.2018.1507278. S2CID 158794287. /w/index.php?title=Valentina_Azarova_(academic)&action=edit&redlink=1 ↩
Grant, Thomas D. (2000). "East Timor, the U.N. System, and Enforcing Non-Recognition in International Law". Vanderbilt Journal of Transnational Law. 33: 273. https://heinonline.org/HOL/LandingPage?handle=hein.journals/vantl33&div=17&id=&page= ↩