Hungary’s constitution bans “Islamization” because the document aims to protect Hungarian language and culture, Prime Minister Viktor Orban said Monday.

Orban also said the constitution forces the government to oppose any kind of mass migration that would endanger those principles.

“To be clear and unequivocal, I can say that Islamization is constitutionally banned in Hungary,” Orban said in parliament at an event celebrating the fifth anniversary of Hungary’s new constitution, now known as the Basic Law.

Orban was quoting from the National Avowal, the Basic Law’s preamble, which details the country’s commitment “to promoting and safeguarding our heritage, our unique language, Hungarian culture” and the protection of “the living conditions of future generations.”

Hungary maintains that the migrant issue is a matter of national sovereignty.

“We have the right to choose whom we want and don’t want to live with,” Orban said.

Hungary has built razor-wire fences on its southern borders to stop migrants from passing through to other European nations. Orban has said he wants “zero” migrants in the East European nation.

Before the fences, nearly 400,000 migrants entered Hungary in 2015 on their way to richer nations in Western Europe.

Hungary has sued the EU at the European Court of Justice to avoid having to take part in an EU plan to resettle migrants. The government is also organizing a national referendum over the EU quotas, meant to rally political support for its anti-immigrant position.