Argentine President Javier Milei announced sanctions against oil companies operating near the Falkland Islands and plans for an integrated naval base in Tierra del Fuego in a nationally televised address, citing what he called a "wind of change" following remarks by US President Donald Trump [3][5][9]. Milei declared the Malvinas "Argentine by history and law" and described the Sea Lion oil project — a deep-sea field approximately 220 kilometres north of the islands being developed by UK-based Rockhopper Exploration and Israel's Navitas Petroleum — as a "clear and present danger" to national security [3][15][21]. He announced a decree to fast-track sanctions under existing Law 26.659, extending penalties to shareholders, directors, and suppliers of companies operating without Argentine authorization, and said those firms would be banned from doing business in Argentina [9][21]. Milei denied the islanders a legitimate right to self-determination, describing them as "a population implanted on usurped territory" [7][15]. Argentina had previously sanctioned Rockhopper in 2013 and Navitas in 2022 [6].

The British government responded across multiple ministries. Defence Secretary Wes Streeting wrote that "the Falklands are British because Falkland Islanders choose to be British" and called the UK's commitment "absolute and unshakeable," adding that Milei's statement "tells us more about domestic politics in Argentina than it does about the Falkland Islands" [1][3][20]. Foreign Secretary Ed Miliband said the islands "will remain so because that is the overwhelming position of the islanders" and vowed to "resolutely uphold" their right to self-determination [7][20]. Downing Street stated that the islanders' right to self-determination "extends to the right to exploit their own natural resources" and dismissed Argentina's economic threats as "nothing new" [15][18]. Conservative leader Kemi Badenoch said "Britain does not surrender to bullies" [15]. Former Falkland Islands Legislative Assembly member Teslyn Barkman said the islands "will remain forever British" [3].

Milei's address followed remarks by Trump, who, when asked whether the US would support Britain in a future Falklands conflict, said "I always review every position. That's just one of many" and complained that Britain "was not there to help me" during the US-led war against Iran [2][10][16][20]. Milei welcomed Trump's comments as "something major" for Argentina's claim and said the US was reconsidering its position because Argentina is "a reliable partner, aligned with Western values" [10][16][20]. A senior US State Department official, Sarah Rogers, posted a photo with Milei saying "exciting things are happening in the Western Hemisphere" [3].

Analysts cautioned against reading Trump's remarks as a deliberate sovereignty shift. Professor Christoph Bluth of the University of Bradford said "Trump has not endorsed Argentina's sovereignty claim; he has merely said the US position is under review" and argued the idea originated inside the Pentagon as leverage over Britain's defence spending and refusal to support US action against Iran [2]. Reader Tilmann Altenberg of Cardiff University described Trump's comments as "first and foremost a reflection on the relationship between the US and the UK, rather than a deliberate shift in US policy" [2]. Political scientist Tomás Mugica of the Catholic University of Argentina similarly saw Trump using the issue to pressure the UK over NATO financing and Iran cooperation [26][33]. Professor Klaus Dodds of Royal Holloway, University of London, said the UK had previously relied on a closer relationship with Washington than Argentina had, but "now that has changed" [2].

Argentine opposition figures accused Milei of using the Malvinas cause for domestic political recovery ahead of the 2027 election. Former Peronist Foreign Minister Jorge Taiana said the measures arrive late after "tres años de persistente desmalvinización" (three years of persistent de-Malvinisation) and concessions that facilitated the UK's advance, and accused Milei of seeking to "galtierise" his image [7]. Buenos Aires Province Minister Carlos Bianco noted that "267 días tardó el fan de Thatcher en cumplir la ley" (it took the Thatcher fan 267 days to comply with the law) [7]. National Deputy Myriam Bregman of the Frente de Izquierda said Milei's strategy "was written by the Pentagon" [7]. Vice President Victoria Villarruel, from the nationalist flank, simultaneously pressured Milei for being too soft on the sovereignty question [3]. Milei's approval rating had fallen to 34 percent [14].

Rockhopper and Navitas stated jointly that "the recent developments are not expected to have a material effect on the development activities of the Sea Lion Project, including the timetable for completion" [3][7]. The companies said their licences were legally granted by the Falkland Islands government with "full UK government support" and that the final investment decision stood, with first oil expected in 2028 [15][21]. Rockhopper's share price fell 7 percent following Milei's address [20]. The Argentine Foreign Ministry rejected the Sea Lion project as unilateral exploitation of resources in an area subject to the sovereignty dispute, citing UN General Assembly resolutions 2065 and 31/49 [21].

Argentine environmental lawyers and war veterans filed a lawsuit challenging the Sea Lion project on sovereignty and environmental grounds. Enrique Viale, president of the Argentine Association of Environmental Lawyers, said "it is colonially occupied territory, and the project is clearly illegal" and that the legal strategy targets "the project's sources of funding" to make exploitation impossible [25]. The plaintiffs argued the project proceeds without Argentine environmental authorization and unlawfully disposes of continental-shelf resources under licences issued by "the British colonial administration" [25].

Chilean President José Antonio Kast, standing alongside Milei in Santiago, called on Britain to open negotiations so that "a quick, peaceful and definitive solution" to the dispute could be found [5][13]. Israeli Foreign Minister Gideon Sa'ar expressed "difficult feelings" over the strain the Navitas involvement caused with London, citing Israel's special relations with Milei [18]. Yair Netanyahu, son of Israeli Prime Minister Benjamin Netanyahu, stated that "the Falkland Islands belong to Argentina" [2]. Former Argentine ambassador to the UK Carlos Sersale argued the Malvinas question should be folded into a broader South Atlantic strategy built around Ushuaia as an Antarctic logistics hub, paired with regional infrastructure development with Chile and Patagonia [17].

Milei's sovereignty defence bill, creating a National Security Council, is being sent to the Argentine Congress, and the decree fast-tracking sanctions under Law 26.659 has been signed [9][21]. Rockhopper and Navitas maintain their drilling timetable, with first oil projected for 2028 [3][21]. The UK government has restated that sovereignty rests with the islanders and that its position is unwavering [15][16].