Quote from the Convention Relating to the Status of Refugees:
Article 31. - Refugees unlawfully in the country of refuge
1. The Contracting States shall not impose penalties, on account of their illegal entry or presence, on refugees who, coming directly from a territory where their life or freedom was threatened in the sense of article 1, enter or are present in their territory without authorization, provided they present themselves without delay to the authorities and show good cause for their illegal entry or presence.
2. The Contracting States shall not apply to the movements of such refugees restrictions other than those which are necessary and such restrictions shall only be applied until their status in the country is regularized or they obtain admission into another country. The Contracting States shall allow such refugees a reasonable period and all the necessary facilities to obtain admission into another country.
Article 32. - Expulsion
1. The Contracting States shall not expel a refugee lawfully in their territory save on grounds of national security or public order.
2. The expulsion of such a refugee shall be only in pursuance of a decision reached in accordance with due process of law. Except where compelling reasons of national security otherwise require, the refugee shall be allowed to submit evidence to clear himself, and to appeal to and be represented for the purpose before competent authority or a person or persons specially designated by the competent authority....
https://www.ohchr.org/en/instruments-mechanisms/instruments/convention-relating-status-refugees
What does Trump have to do to get the US out from under the Refugee Convention?
Send (or hand deliver) the Secretary-General of the United Nations Antonio Guterres a letter!
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Dear Secretary-General of the United Nations:
I, Donald J. Trump, the President of the United States, on behalf of the United States, do denounce the 1951 Convention Relating to the Status of Refugees and its 1967 Protocol, as permitted by Article 44.
Donald J. Trump