The North Atlantic Treaty Organization (NATO) does not foresee any mechanism to expel a member country. The only procedure included in its founding treaty (1949), in its article 13, allows for the voluntary withdrawal of a member country, with notification to the United States and a one-year notice period, but it does not contemplate expulsions. Unlike other international organizations, NATO does not include in its legal framework sanctions in that sense, nor suspension procedures that lead to expulsion.
In this way, Donald Trump's recent threats about a possible expulsion of Spain from the Alliance clash with the organization's legal framework. The background of the US warnings revolves around the disagreement on defense spending with Pedro Sánchez's Executive, as well as the political alignment of the Spanish government, but the treaty is clear: no ally can be kicked out of NATO, regardless of the political or military tensions that may arise within the Alliance.
The only way: voluntary exit
In this way, the only existing mechanism for an exit from NATO is the one set out in Article 13, which marks a procedure with three keys:
- The decision to leave NATO is unilateral, it depends exclusively on the country.
- A formal notification to the Government of the United States, the depositary of the treaty, must be made.
- The withdrawal becomes effective one year after the notification.
Unprecedented formal output
In more than seven decades of NATO history, no country has formally activated the withdrawal mechanism. There have been cases of partial disengagement, such as France in 1966, which left the integrated military structure, and Greece in 1974, which temporarily withdrew its forces from military command.
However, in both cases the countries remained full members of NATO.
Although, as we have seen, NATO does not allow expelling a country, the United States, as the main power of the Alliance, has tools of pressure, without violating the treaty, to push a country like Spain towards a voluntary exit from the Alliance: political, military, and economic levers; indirect ways to force a de facto exit.
Political and diplomatic pressure
NATO works by consensus and being isolated reduces a country's real weight within the Alliance. The US can resort to:
- Public statements that question Spain's commitment.
- Isolation in key decisions within the North Atlantic Council.
- Blocking of consensus where Spain needs support.
Military pressure: bases and cooperation
Spain hosts key strategic infrastructures for the US, such as the Rota or Morón bases. This opens another avenue of pressure:
- Review or reduction of the US military presence.
- Withdrawal of strategic capabilities.
- Less cooperation in intelligence or defense.
It not only has a military impact, but also an economic and geopolitical one for Spain.
Indirect economic pressure
The US could exert indirect pressure on Spain with real effects on the economy:
- Commercial or tariff measures.
- Less support in international economic forums.
- Pressure on strategic investments or companies.
Condition Spain's role within NATO
Another way to exert pressure is to reduce Spain's operational weight in the Alliance without expelling it:
- Less access to sensitive information.
- Exclusion from strategic or technological projects.
- Limitation of leadership in missions.
This would generate a “low-level belonging” that could make it less attractive to continue within. All these levers would aim to push a sovereign decision, creating a context that pushes for a voluntary decision.