US President Donald Trump’s suggestion that Ukraine should recognize Russia’s control over Crimea, the southern Ukrainian peninsula that Moscow annexed more than a decade ago, is threatening to upend international law and order.
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Is this legal?
No. If the Trump administration was to somehow recognize Russian sovereignty over Crimea, it would be breaching international law as well as multiple declarations and agreements made by the United States, including by the first Trump White House.
“In terms of international law, such a pronouncement would be null and void,” said Sergey Vasiliev, an international law expert and professor at the Open University in the Netherlands.
“That territorial acquisitions that result from the use of force shall not be recognized as legal is basically one of the bedrock principles of international law,” Vasiliev told CNN.
Recognizing Crimea as part of Russia would put the Trump administration in breach of the 1994 Budapest Memorandum, in which the US made a commitment to respect Ukraine’s sovereignty and borders, in exchange for Kyiv giving up its nuclear weapons.
In 2018, during the first Trump administration, then-Secretary of State Mike Pompeo issued a statement reaffirming the US’ refusal to recognize the Kremlin’s claims of sovereignty over Crimea.

https://www.cnn.com/2025/04/25/world/trump-ukraine-crimea-explainer-intl