Measures designed to safeguard NATO may not be as ironclad as their architects intended. When Congress passed a law in 2023 requiring Senate or Congressional approval for the U.S. to exit NATO, the move was hailed as a bipartisan triumph for the transatlantic alliance. But with Donald Trump eyeing a return to the Oval Office, that victory could be tested—and circumventing these safeguards might be easier than it appears.
Congress vs. the Presidency: A Constitutional Standoff
In a rare show of bipartisanship, Senators Tim Kaine (D-Va.) and Marco Rubio (R-Fla.) spearheaded legislation to block unilateral presidential decisions about NATO withdrawal. The provision, included in the Fiscal Year 2024 National Defense Authorization Act (NDAA), requires a two-thirds Senate majority or a separate Congressional act to approve such a move. President Biden signed the measure into law, signaling robust support for NATO across party lines.
But legal scholars caution that this law is far from a silver bullet. Scott Anderson, senior editor at Lawfare and a Brookings Institution fellow, warns it could spark a constitutional showdown between Congress and the executive branch.
“This isn’t a cut-and-dried issue,” Anderson explains. “Congress can tell the president, ‘You can’t do this,’ but if the president ignores that directive, it becomes a power struggle likely destined for the courts.”
The Supreme Court’s Reluctance to Intervene
A key complication lies in the judiciary’s traditional aversion to arbitrating disputes between the legislative and executive branches. Historically, the U.S. Supreme Court has treated such clashes as political, not legal, questions. University of Chicago law professor Curtis Bradley notes that for any case to proceed, there must be a plaintiff with standing.
“The only viable plaintiff I can envision is Congress itself. But it’s unclear whether Senate Republicans would back such a lawsuit,” Bradley argues.
To bolster the law, experts suggest Congress could explicitly authorize legal action in cases of noncompliance, potentially increasing the judiciary’s willingness to weigh in on the matter.
Who Could Sue? Exploring Alternative Paths
While Congress is the most obvious litigant, Anderson speculates that other parties, such as military personnel or private citizens with investments in NATO countries, might attempt to sue. However, their standing would likely be challenged, making their legal claims tenuous.
Alternatively, if Congress remains divided, a single chamber could theoretically initiate legal action—though this approach also raises thorny questions about legitimacy and authority.
Even if a case reaches the Supreme Court, its outcome is anything but predictable. Anderson characterizes this as “uncharted legal territory,” noting that Congress has never directly confronted a president over treaty withdrawal in court. Without historical precedents, the judicial branch would be venturing into unknown waters.
Trump’s Track Record: A Preview of What’s to Come?
Donald Trump’s disdain for NATO is no secret. During his presidency, he repeatedly lambasted allies for what he saw as their failure to pull their weight, particularly in defense spending. His critiques often veered into outright threats, raising questions about the U.S.’s commitment to the alliance.
Trump’s actions in other contexts offer a glimpse of what NATO might face. In 2020, his administration unilaterally withdrew the U.S. from the Open Skies Treaty, defying Congressional directives that required prior notification. At the time, Trump’s legal advisors argued that the president’s constitutional authority in foreign policy superseded legislative attempts to constrain him.
“The president’s powers to withdraw from treaties stem from his role as the sole representative of the nation in foreign affairs,” asserted Steven Engel, then head of the Justice Department’s Office of Legal Counsel.
While such arguments remain contentious, they underscore the potential challenges Congress could face in enforcing its NATO safeguards.
The Stakes: A Crisis of Trust and Stability
Even if the U.S. remains in NATO on paper, the mere act of announcing withdrawal could send shockwaves through the alliance. As Camille Grand, a former NATO assistant secretary general, noted, “De facto, the day you send the letter, it’s already effectively in motion.”
The ripple effects would extend beyond diplomacy. The U.S. would need to address the future of over 100,000 troops stationed in Europe and the fate of NATO’s command structure, which has been led by American generals since the alliance’s founding in 1949.
And the timing couldn’t be worse. “We’re not debating this in a vacuum,” Grand emphasized. “There’s a war in Europe. Many European allies fear a deeper confrontation with Russia, and any sign of U.S. disengagement could embolden aggression.”
The Bigger Question: America’s Role in the World
Trump’s rhetoric may have pressured NATO allies to increase defense spending—he frequently touted the “billions and billions” they added to their budgets—but his tactics also frayed trust within the alliance. By framing burden-sharing as a condition for U.S. support, he undermined NATO’s core principle of collective defense enshrined in Article 5 of its charter.
As former NATO Secretary General Anders Fogh Rasmussen observed, “During my visit to Congress, I saw strong bipartisan support for NATO. While a U.S. president can create significant challenges for the alliance, a full withdrawal? That’s highly unlikely.”
Yet the prospect of Trump’s return to power in 2025 has European allies on edge. His past threats and suggestions of “resetting” America’s role in NATO have cast a long shadow over the alliance’s future.
Trump’s unconventional approach may have yielded short-term wins, such as increased defense budgets. But his reliance on threats and ultimatums has left deep fractures in transatlantic unity—cracks that could prove costly for NATO in an increasingly volatile world.
NATO Withdrawal: Scenarios, Risks, and Loopholes for Trump
If Donald Trump returns to the White House, his long-standing skepticism toward NATO could reignite debates about the alliance’s future, making it a centerpiece of U.S. foreign policy. Despite legal barriers meant to prevent unilateral action, Trump may still find ways to undermine the alliance without formally withdrawing.
With the possibility of Trump reclaiming power, NATO’s stability faces not only political pressure but also a legal conundrum that could reshape the balance of authority within the U.S. government.
Legal Barriers and the "One-Year Waiting Period"
The formal process for withdrawing from NATO is governed by a "notice of denunciation," which must be submitted to all member states. Official withdrawal would take effect one year after the notice is filed, allowing time for potential diplomatic reversals.
However, legal safeguards alone may not deter a president intent on weakening the alliance. Democratic lawmakers warn that Trump could bypass formal withdrawal by undermining NATO through indirect means: freezing ambassadorial appointments, scaling back U.S. troop participation in military exercises, or slashing funding for alliance operations.
Democratic Response: Fortifying the Alliance
Recognizing the risks posed by Trump's rhetoric during his first term, Congress moved to establish legislative safeguards. Senator Chris Van Hollen (D-Md.) underscored the importance of NATO and praised bipartisan efforts to shield it from unilateral executive action.
“After Trump’s threats in his first term, Congress—understanding NATO’s critical role—acted on a bipartisan basis to ensure the president cannot withdraw unilaterally,” Van Hollen stated.
Senator Tim Kaine (D-Va.), co-author of the legislation protecting NATO, expressed deep concern over Trump’s past statements.
“U.S. security is strongest when we work alongside our allies,” Kaine said. “Trump’s dismissive remarks about NATO send a dangerous message.”
Legal and Historical Precedents
Trump’s potential maneuvers against NATO wouldn’t be unprecedented. In 2020, his administration unilaterally withdrew from the Open Skies Treaty, disregarding Congressional requirements for prior notification. At the time, Trump’s legal advisors argued that the president’s constitutional authority in foreign policy allowed him to bypass such restrictions.
“The president’s authority to withdraw from treaties derives from his role as the sole organ of the nation in foreign relations,” claimed Steven Engel, a legal advisor to the Trump administration.
But this perspective is not universally accepted. Curtis Bradley, a University of Chicago law professor, argues that Congress holds a clear right to regulate international treaties and that Trump’s legal team failed to convincingly argue otherwise.
“Presidents face a significant burden of proof when claiming a law’s unconstitutionality as a basis for ignoring it,” Bradley explained.
Real-World Implications: Trust and Troop Deployment
Even without formal withdrawal, merely signaling an intention to leave NATO could shake the alliance to its core. As Camille Grand, a former NATO assistant secretary general, explained, “De facto, the day you send the letter, it’s already effectively in motion.”
The ripple effects of such a move could extend far beyond diplomacy. The U.S. would face questions about the future of over 100,000 troops stationed across Europe and the alliance’s command structure, which has been led by American generals since NATO’s inception in 1949.
“We’re not discussing this in a calm environment,” Grand noted. “There’s an ongoing war in Europe, and many European allies fear that confrontation with Russia could escalate further.”
Political Threats and Pressure on Allies
During his first term, Trump frequently criticized NATO allies for failing to meet the alliance’s defense spending target of 2% of GDP. His rhetoric often turned into outright threats, calling into question the U.S. commitment to collective defense.
“If we’re not paying, will you still protect us? … Absolutely not,” Trump said at one of his rallies, a remark that underscored his transactional view of U.S. alliances.
Trump’s approach succeeded in pressuring allies to boost defense budgets—something he proudly touted as a personal victory. However, critics argue that his combative tactics eroded trust within the alliance and undermined NATO’s foundational principle of shared defense.
What’s Next?
Trump’s return to the White House could pose an existential challenge to NATO. Legal barriers, while meaningful, may be insufficient to prevent a determined president from reshaping America’s role in the alliance—or sidelining it entirely.
Amid a war in Europe and escalating tensions with Russia, NATO’s stability is more than a foreign policy issue; it’s a linchpin of global security. Trump’s unpredictable approach, though effective in forcing short-term changes, risks leaving behind long-term fractures that could compromise the alliance’s unity in the face of mounting threats.
Trump and NATO: A Geopolitical Dilemma Threatening Alliance Unity
Donald Trump has never openly declared an intention to pull the United States out of NATO, but multiple reports indicate that he floated the idea privately throughout his presidency. On the campaign trail, he often lambasted allies for failing to meet NATO’s defense spending goals, arguing that the U.S. shouldn’t be expected to defend countries that, in his view, shirk their financial commitments. In a particularly provocative moment, Trump even suggested he might “encourage” Russia to take action against NATO members that fall short of the alliance’s budgetary targets.
According to POLITICO, Trump told European Commission President Ursula von der Leyen in 2020 that the United States would not come to Europe’s defense in the event of military aggression. His rhetoric was rooted in a belief that only the threat of abandonment could force allies to step up their military investments. Trump has claimed that his hardline approach led to NATO members increasing their defense spending by “billions and billions of dollars.”
These statements ignited controversies within both the American political system and the broader international community. Critics, particularly Democrats and several NATO allies, argue that Trump’s rhetoric and threats undermined trust in the U.S. as the cornerstone of the alliance. On the other hand, Trump loyalists, including some Republicans, hailed the strategy as a pragmatic success, crediting it with pushing NATO members to prioritize defense spending.
The Long-Term Implications
Trump’s transactional view of alliances has sparked concerns about America’s broader strategic vision. While both NATO advocates and critics agree on the need for allies to meet defense spending commitments, Trump’s framing of these commitments as preconditions for U.S. support directly challenges NATO’s core principle of collective defense, enshrined in Article 5 of its charter.
This stance has left NATO allies wary of American reliability and raised questions about the U.S.'s long-term intentions within the alliance. Former NATO Secretary General Anders Fogh Rasmussen highlighted the significance of legislative safeguards introduced by Congress to prevent unilateral presidential withdrawal.
“During my visit to the U.S. Congress, I observed strong bipartisan support for NATO and the importance of maintaining U.S. membership in the alliance,” Rasmussen said in an interview. “The U.S. president can certainly create significant challenges for NATO as commander-in-chief, but a full withdrawal? That’s highly unlikely.”
Yet, as Rasmussen noted, while Congress can block a formal exit, a president with anti-NATO leanings could still create instability by curbing U.S. participation in alliance activities.
European Concerns Over a Possible Trump Return
Despite legislative protections, the prospect of Trump’s return to power in 2025 is causing unease among European leaders. His repeated threats and allusions to “resetting” America’s role in NATO have cast a shadow over the alliance’s future. Many allies fear that his reelection could embolden Russia or exacerbate divisions within NATO.
Trump’s unorthodox approach, paradoxically, achieved some of its short-term goals: NATO members increased their defense budgets significantly during his tenure. However, this came at a steep cost to transatlantic unity. By using ultimatums and public shaming as leverage, Trump introduced a sense of mistrust that could prove detrimental to NATO’s long-term cohesion.
A Fragile Future
The stakes for NATO couldn’t be higher. In the face of ongoing war in Europe and heightened tensions with Russia, the alliance represents a vital bulwark of global stability. While Trump’s focus on burden-sharing brought about tangible results, his methods—and the lasting divisions they created—leave NATO at a crossroads. Should Trump return to the White House, the future of the world’s most powerful military alliance may hang in the balance.