Ukraine could join NATO with occupied territories excluded from Article 5

The question of whether Ukraine can join NATO while parts of its internationally recognised territory remain under Russian occupation has moved from theoretical debate to practical diplomacy. As Donald Trump prepares to return to the White House with a stated intention of ending the war quickly, the alliance faces a choice: maintain the unwritten rule that territorial disputes bar membership, or adapt its founding treaty to reflect a reality in which Russia has effectively weaponised that rule.

Luke Coffey, a senior fellow at the Hudson Institute, argues that NATO already possesses the legal tools to admit Ukraine without surrendering the principle of collective defence. The mechanism lies in Article 6 of the 1949 North Atlantic Treaty, which defines the geographic scope of Article 5 guarantees. That article has been amended before. It can be amended again.

The Article 6 precedent

Article 6 currently limits collective defence to the North Atlantic area north of the Tropic of Cancer. This excludes US territories such as Guam and Hawaii, the United Kingdom's Falkland Islands and France's Réunion. The exclusion of overseas territories is not an anomaly; it is a deliberate design feature. When Greece and Turkey joined in 1952, Article 6 was amended to include them. In 1963, after Algerian independence, the North Atlantic Council acknowledged that Article 6 no longer applied to the Algerian departments of metropolitan France.

Coffey's proposal is straightforward: during the accession protocol process, NATO members would amend Article 6 to exclude those Ukrainian regions currently under Russian control. The rest of Ukraine, within its 1991 borders, would receive full Article 5 protection. The occupied territories would remain under Ukraine's sovereignty in international law but would not trigger a collective defence response if attacked.

This is not a novel invention. The North Atlantic Treaty explicitly allows for amendment by consensus. The precedent of 1952 and 1963 demonstrates that the alliance has adjusted its geographic scope when political circumstances demanded it.

The West Germany model

The political template already exists. On the eve of its accession in 1954, West Germany declared that it would "undertake never to have recourse to force to achieve the re-unification of Germany or the modification of the present boundaries of the Federal Republic of Germany, and to resolve by peaceful means any disputes." That declaration did not renounce the legal claim to lost territories; it renounced the use of force to recover them. The distinction mattered. It allowed the Federal Republic to join NATO while the German Democratic Republic remained under Soviet control, and while the Oder-Neisse line remained contested.

Zelenskyy has already signalled openness to a similar pledge. In public remarks he has spoken of ending the "hot phase" of the war in exchange for NATO membership, implying a willingness to pursue the return of occupied territories through diplomacy rather than arms. A formal non-use-of-force declaration, modelled on the 1954 text, would satisfy the alliance's requirement that new members settle disputes peacefully.

The 1995 Study and the misconception it created

Opponents of Ukrainian membership while territory is occupied often cite the 1995 Study on NATO Enlargement as a binding prohibition. The study states that countries with ethnic or external territorial disputes "must settle those disputes by peaceful means in accordance with OSCE principles. Resolution of such disputes would be a factor in determining whether to invite a state to join the alliance." The word "factor" has been read as "precondition" by generations of diplomats and analysts.

Coffey argues this is a misreading. The study does not say resolution is the sole factor, nor does it say an invitation cannot be extended before resolution. It says resolution would be "a factor", one consideration among many. The Study on NATO Enlargement remains the alliance's foundational enlargement document, but its language is permissive, not prohibitive.

Estonia and Croatia: membership without settled borders

The alliance's own practice supports the permissive reading. Estonia joined NATO in 2004 despite lacking a legally ratified border treaty with Russia. The two countries signed a border agreement in 2005, but Russia withdrew its signature after Estonia's parliament attached a preamble referencing Soviet occupation. The treaty was eventually ratified in 2014, a decade after Estonia's accession. Croatia joined in 2009 with unresolved maritime and land border disputes with Serbia, some of which remain unsettled today.

Neither case triggered a crisis. The alliance accepted that border disputes, while undesirable, need not be fatal to membership provided the applicant commits to peaceful resolution. Ukraine's commitment would be formalised in the non-use-of-force pledge.

Why European security forces are not a substitute

Speculation in European capitals has centred on the possibility of a post-war European security force deployed to Ukraine, perhaps under EU or bilateral auspices, to avoid direct NATO involvement. Coffey dismisses this as naive. French, British or German troops coming under Russian attack would inevitably trigger a NATO response, whether or not they operated under a NATO flag. The alternative, the alliance standing aside while its members' forces are attacked, would destroy NATO's credibility more surely than any Russian missile.

This logic drives the argument for full membership. If European troops are going to be at risk in Ukraine, they should be covered by Article 5. If they are covered by Article 5, Ukraine should be in NATO. The detour through a non-NATO force merely adds ambiguity without reducing risk.

The political will deficit

The legal and historical arguments are coherent. The obstacle is political. Amending Article 6 requires consensus among all 32 allies. Several members, particularly those bordering Russia, have historically opposed any move that could be portrayed as legitimising territorial conquest. Others fear that partial Article 5 coverage creates a two-tier membership that weakens the alliance's deterrent posture.

There is also the question of US leadership. Trump's return introduces volatility. His scepticism of NATO is well documented; his desire for a quick deal with Moscow is explicit. Whether his administration would expend political capital to shepherd an Article 6 amendment through the North Atlantic Council is uncertain. European leaders, for their part, have spent two years calibrating support to avoid escalation. Asking them to endorse a structural treaty change that Moscow will denounce as escalation is a different order of demand.