This month, Portuguese prosecutors opened an investigation into whether the center-right government of Prime Minister Luís Montenegro legally authorized the United States to use the Lajes Air Base in the Azores during the war on Iran. The probe was triggered by a complaint from the Left Bloc that opposed the war.

This is the kind of story that has implications beyond Lisbon. At issue is a question: when partners in the Western alliance facilitate American military operations, who decides whether that participation is lawful—and can anyone hold them to account?

A 1951 bilateral defense treaty allows Washington to use Lajes without prior authorization during peacetime. The base is a pillar of the U.S. force-projection architecture, a strategic transit hub hosting the 65th Air Base Wing and supporting U.S., NATO, and allied operations. But once hostilities begin, Portugal must explicitly approve its use.

Unlike neighboring Spain—where Pedro Sánchez’s center-left government refused the use of U.S. bases to attack Iran and condemned the war as contrary to international law—Lisbon authorized several U.S. transit flights through the base. That decision drew sharp criticism from left-wing parties and ignited a domestic debate over Portugal’s complicity in a conflict it insists it is not part of.

Reacting to the launched inquiry, Prime Minister Montenegro defended Lisbon’s decision, arguing that the use of the base was “fully legal” and urged the judiciary “not to make political judgements.” Earlier, Foreign Minister Paulo Rangel said that he considered “everything done to re-open the Hormuz Strait and secure the maritime freedom as a positive,” while emphasizing that Portugal was not involved. And recently, on a visit to Lisbon, standing alongside his Portuguese counterpart, U.S. Secretary of State Marco Rubio insisted that Washington had “adhered to the protocols” regulating the use of the base.

Unlike in some other countries, where prosecutors enjoy broad discretion to decline cases, in Portugal they are bound by the principle of legality: they must investigate when there are sufficient grounds. Contrary to Montenegro’s insinuations , the investigation is not a political stunt. It is the law working as designed.

That is precisely why the probe is worth watching—and why it may ultimately disappoint.

“It is a good thing that it’s being scrutinised, but plenty of things get scrutinized to no avail,” notes, in an interview from Lisbon, Ghoncheh Tazmini, author of Power Couple: Russian-Iranian Alignment in the Middle East , a Fellow of the UK-based Royal Historical Society, and currently working on a book on the Strait of Hormuz. “There’s a deeper political reality that determines these matters, regardless of the legal arguments.”

That deeper reality is worth naming. As Tazmini puts it: “Portugal’s response illustrates the gap between formal sovereignty and genuine strategic autonomy. Despite its legal authority to impose conditions (on the use of Lajes), Lisbon has shown little willingness to depart from Washington’s strategic priorities, revealing how deeply entrenched alliance dependencies continue to shape Portuguese foreign policy.”

Ana Gomes , a retired Portuguese diplomat and a former presidential candidate , is even more direct. She rejects the government’s legal justification outright. “Abundant evidence demonstrates that President Trump’s actions against Iran were neither defensive nor proportionate. They were illegal acts of aggression, clearly violating the UN Charter and international law”, she said to FPIF. She calls the Portuguese government’s position “mere disingenuous hypocrisy to dismiss questions.”

Gomes points to a telling admission. “Rubio declared last May to Fox News that the Portuguese authorization was obtained by the United States ‘even before Portugal was informed about what would be the U.S. request.'” For Gomes, this “clearly shows that Portugal preferred not to know.”

She is equally skeptical that the investigation will produce accountability, invoking a precedent that haunts Portuguese debates over complicity in American operations. Portugal’s governments under Prime Ministers Durão Barroso (center-right) and José Sócrates (center-left) authorized the CIA’s rendition program under President George W. Bush “war on terror.” The program abducted “illegal combatants” and transported them to U.S.-controlled sites for interrogations that included torture. Portugal’s airspace and airports were heavily utilized to facilitate the illegal transfer and kidnapping of terrorism suspects.

As a former member of the European Parliament, Ana Gomes played a key role in exposing that complicity. That experience doesn’t make her feel optimistic about the Iran war probe: “At some point the attorney general will order closure, to serve the government, regardless of the collected evidence of human rights and international law violations and the government and state officials responsible for them.”

Gomes also disputes the premise that Portugal’s choices should always be determined by its strategic dependence on Washington. “Portugal has a strategic dependence on the integrity and reinforcement of the European Union, as its member state, not on the United States”, she said to FPIF.

The subservience, she argues, “serves the interests—namely economic interests—of parts of Lisbon’s establishment, both political and military,” now compounded by “fear of facing the erratic retaliations and bullying from the Trump administration, be it tariffs, disputes over NATO financial contributions or claims over some strategic territory of the allies (in a thinly-veiled reference to the Azores archipelago in the Atlantic).” Unlike Sánchez, she adds,

Portugal’s leadership believes that by appeasing Trump it might escape his ire.

Yet the Lajes probe still matters, for three reasons.

First, it exposes the fiction that junior partners are mere bystanders. Portugal did not object to the flights. It made a choice. The investigation forces Lisbon to defend that choice in legal terms, not just diplomatic ones—and that is a form of accountability, however partial.

Second, it highlights the asymmetry embedded in the Atlantic alliance. The United States can use bases, transit airspace, and stage operations with assurances that are often unverifiable. Portugal, meanwhile, absorbs the political and legal risk.

Third, it connects to a deeper question about European strategic autonomy. In her tenure in the European Parliament, Gomes recalls, she was pushing to develop the EU’s own security and defense capabilities. Instead, she argues, “the military and political establishments in several member states resisted it, pretending that NATO alone could take care of our defense.”

That, in effect, has sealed Europe’s self-vassalization. If a superpower can use a junior partner’s territory to wage an illegal war without any effective limits and verification, sovereignty becomes hollow. The Lajes controversy is but one symptom of this larger disease—just like the rendition flights were a decade ago.

And yet, the probe is a revealing test. Its fate will determine whether a 1951 treaty and a prosecutor’s obligation to investigate can meaningfully constrain a superpower—or whether, as history suggests, the deeper political reality will prevail again.

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