Every ESA Country Has Now Signed the Artemis Accords. Except One.

The Artemis Accords are not a treaty, not a law, and not a club with bylaws. They are a set of principles — safe and sustainable exploration, transparency, deconfliction of activities, preservation of heritage sites — that each signatory adopts unilaterally. No UN vote. No binding obligation. Just a mutual understanding of how nations should behave on the Moon, written in Washington and signed by countries that want a seat at the table where those rules get written. That table just got a lot more crowded.

Ireland and Malta signed the Accords on May 4, becoming the 65th and 66th nations to do so. The what-and-why comes first: the European Space Agency now has a complete lineup in the U.S.-led lunar governance framework, after four years of diplomatic arm-twisting that produced nothing until Artemis II flew. The who-and-when is context.

Five countries signed in 15 days — Latvia on April 20, Jordan on April 23, Morocco on April 29, then Malta and Ireland on May 4. The common thread is the crewed Orion loop around the Moon in early April, the first in more than five decades. A spacecraft that launches on time, loops behind the Moon, and comes home successfully tends to change the calculus for the next round of fence-sitters.

"As the international community sees the success of the program as it moves forward, it's only going to become more and more popular," Mike Gold, president of Redwire Space and a former NASA official who helped draft the Accords, said in an April 29 speech.

Gold's confidence is warranted, but the Accords remain a bilateral framework, not a treaty. Each new signatory makes a unilateral commitment to principles without creating any binding legal obligation. Critics, including two researchers writing in Science magazine's Policy Forum, have argued this structure lets the U.S. lock in its interpretation of the Outer Space Treaty without the negotiating process the UN normally requires.

That tension hasn't stopped the surge. Ireland's Minister for Enterprise, Tourism and Employment Peter Burke signed at NASA Headquarters in Washington, with NASA Administrator Jared Isaacman and State Department officials witnessing. Burke's emphasis was on cooperation and resilience. "We need to continue to support this exciting infrastructure that is core to communications, to our security," he said at the ceremony.

Malta's signing happened hours earlier in the Maltese city of Kalkara, witnessed by NASA and State Department representatives. Malta's Minister of Education, Youth, Sports, Research and Innovation Clifton Grima framed it in economic terms: governance credibility, investment attraction, and quality jobs in the space economy.

With Ireland's signature, every full member of the European Space Agency has now signed the Accords. That took four years of sustained diplomatic engagement, multiple NASA and State Department visits to European capitals, and what several sources describe as considerable arm-twisting at ESA council meetings. The United States wanted a unified European front before the lunar base design gets locked in and the question of who sets norms for lunar activity gets settled by default.

The only EU member state that hasn't signed is Croatia. No government official in Zagreb has explained why, and nobody in the State Department or NASA is saying so publicly. Croatia has been silent through the entire ESA signatory drive. No statements, no reported negotiations, no objections filed with the UN. That silence is itself a signal. Either Croatia is holding out for terms it hasn't disclosed, or it has decided the Accords are not worth the domestic political cost of joining. Either way, it is the one hole in what is otherwise a near-complete map of Western space-faring nations aligning with the U.S. lunar governance framework.

The ESA closure matters beyond Europe. India, Brazil, South Africa, and the UAE are among the significant space-faring nations that remain outside the Accords. With Europe locked in, the State Department's diplomatic focus will shift to these holdouts — and the window for them to negotiate governance influence is narrowing. Once a critical mass of nations has signed, the Accords become the de facto baseline and alternative frameworks like China's International Lunar Research Station become the deviation. That is when the terms get set. Fence-sitters who wait too long end up choosing a framework someone else designed rather than having a voice in designing either.

The cheap-signaling critique has teeth for nations like Malta and Ireland, which have no independent launch or lunar programs. They gain a seat at a conference table that does not yet exist, for commitments that carry no legal force. What they actually receive in return is access to NASA cooperation, data-sharing agreements, and the political goodwill of the State Department. Whether that constitutes genuine governance influence or a flagship gesture depends on whether the Artemis lunar base program actually materializes and whether the U.S. follows through on its stated commitment to multilateral decision-making.

For VCs, founders, and engineers building toward the Moon, the ESA closure is a signal: the regulatory and diplomatic scaffolding for lunar activity is being built around the Accords framework, not around any alternative. Supply chains, data agreements, safety standards, and bilateral cooperation will increasingly map onto signatories. A company structuring a lunar logistics contract, or a research institution negotiating a data-sharing agreement with a foreign partner, will find that the other party's signature on the Accords shapes the legal and diplomatic context of that agreement. That is not guaranteed leverage. But it is a narrowing of the alternative landscape.

The counterargument is real: the Accords are nonbinding, offer limited tangible benefit to smaller signatories, and cede some degree of autonomy to a framework designed in Washington. Space-faring nations that want to stay clear of U.S.-led structures have built their own. Countries that signed may get a seat at a table that doesn't yet exist, for an agenda they didn't write.

But the Artemis II result changed the calculus for fence-sitters. A crewed lunar mission that launches on time, loops behind the Moon, and comes home successfully is a proof of concept that cannot be argued away. The Accords were always about the long game. Now that the program has demonstrated it can fly, the long game looks like it might actually arrive, and the diplomatic window to shape it is closing faster than it opened.

Croatia has not commented publicly on its decision not to sign. The question of why one EU country is sitting out the most comprehensive alignment of Western space policy in decades is one Zagreb seems determined to leave unanswered.