Prime Minister Viktor Orban of Hungary is at his best when defending his nation’s sovereignty against encroachment, be it from the liberal progressivism of George Soros or the crushing intrusions of the European Union.

He’s at his worst, however, when interfering in the self-determination of other sovereign nation-states around him.

Most will admit—although in many places only grudgingly—that Orban won the intellectual argument over mass migration. The open-door policy embodied by German Chancellor Angela Merkel has been discredited as a mistake.

All across Europe—from EU Commission President Jean-Claude Juncker to French President Emmanuel Macron—both the rhetoric and policy decisions on immigration have swung against the open-door policy that Merkel and EU elites championed during the height of the migration crisis in 2015.

As we’ve seen in recent elections in Austria and the Czech Republic, candidates and parties that share Orban’s mix of populism, Euroscepticism, and unapologetic defense of national sovereignty have defeated establishment politicians.

Merkel herself fared badly in elections last month. Her Christian Democratic Union/Christian Social Union in Bavaria alliance dropped from 311 seats in the Bundestag and 41.5 percent support at the previous election to 246 seats and 32.9 percent support.

Merkel is likely to remain chancellor under a new coalition, but she is weak.

Orban’s Fidesz party is itself looking buoyant ahead of elections to be held next spring. If he does remain prime minister, he should have potential allies not just in Austria and the Czech Republic, but also in Slovakia and Poland.

But unfortunately, Orban is stirring trouble with Ukraine and Romania.

What’s the issue? You can put many different names on it—minority rights, multiculturalism, diversity—but some would say it borders on “irredentism.” Britannica describes irredentism as a “territorial claim based on a national, ethnic, or historical basis.”

Hungary lost a great deal of territory and citizens in the last century, first at the Treaty of Trianon in 1920 and then after World War II.

Without going into much history (which you can find here), today’s situation is that there are around 156,000 Hungarian speakers (or ethnic Hungarians) living in Ukraine, and around 1.5 million in the much smaller nation of Romania, with scattered numbers in others nations like Serbia, Croatia, and Slovakia.

The problem? Ukraine passed a law last month that would require most Ukrainian secondary schools to be taught in the Ukrainian language. It allows school children to undergo education in other languages in primary school, but shifts them toward Ukrainian in secondary school.

This will affect the ethnic Hungarian children living in Ukraine, many of whom are not fully fluent in Hungarian, according to reports. In protest of the policy, Orban urged European foreign ministers earlier this month to revise the EU’s partnership deal with the Ukraine.

Hungarians really, really hate it when non-Hungarians tell them to “just get over it,” and we will not do that here. But this new Ukrainian law seems to take a reasonable approach.

A country has the right to promote its unity, and language is the best way to do it. If a government treats different ethnicities as second-class citizens, it should of course be called out and shamed on the international scene.

Ukraine is likely much more concerned with the presence of more than 8 million ethnic Russians—and 14 million whose mother tongue is Russian—within its borders than with the 156,000 Hungarians, especially since Russian President Vladimir Putin uses them as an excuse to wage war with Ukraine.

Given the geopolitical stakes, Hungary’s threat to derail Ukraine’s relations with the West unless it rescinds its language law is churlish at best.

Orban’s government is also stoking long-term trouble by trying to entice the much larger group of ethnic Hungarians in Romania, mostly in Transylvania, to adopt dual nationality and register to vote in next year’s election in Hungary.

Budapest also wants these very same ethnic Hungarians to vote in Romania as well—for the Democratic Alliance of Hungarians in Romania (UDMR) party, which represents the Hungarian minority.

These are the problems the West has courted by permitting dual nationalities, a process much further advanced in Europe than in the U.S.

Europe is filled with these cases. There are Catalan and Basque speakers on both sides of the Spanish-French border, Galician speakers in Portugal, German speakers in France—and if all states made these groups’ existence an issue, there would be no end in sight.

We Americans could just cross our arms and thank our lucky stars we don’t have this history, but a chief U.S. foreign policy goal is a stable Europe. We have an interest in seeing that these tensions subside.

Orban understands the power of language and ethnic identity all too well, which is obviously why he wants Hungarian speakers to maintain their strong emotional links to the “motherland.”

He recently told an interviewer that autonomy for Hungarian-speaking regions in neighboring countries “is a goal that is much disputed, but the Hungarians have neither the means nor the opportunity to give up on it.”

The question obviously arises: Does he expect the lands Hungary lost to be returned at some future date? It is a question no doubt many ask in Bucharest, Kyiv, and other nearby capitals.

Orban should add diplomacy to his skills and propose ways in which the interests of ethnic minorities throughout the region might be protected while also taking into account the national government’s interest in unity.

Orban speaks for many in Europe who see their destiny as a continent of strong and confident sovereign nation-states. But being captured by the burdens of the past now threatens to undermine that destiny.