Denmark’s requirements for an immigrant to become a citizen are fairly typical of immigration laws around the world: the applicant must have legal residence for up to nine years, pass a Danish language test, have no record of serious crime, be financially self-sufficient, and pass a test on Danish politics, history and society.

Now, Denmark is adding one more requirement to that list, and it would seem, for most people, to be a piece of cake: the new citizen must shake hands with the person giving him the citizenship oath.

But something so simple is turning into an issue of religious liberty. Many aspiring Danish citizens are immigrants and refugees from predominantly Muslim nations. A gesture that Danes see as a de rigeur sign of mutual respect is for Muslims fraught with delicate sexual mores.

Highly observant Muslims believe that bodily contact between the sexes should be reserved for members of one’s immediate family. Men and women outside of that circle do not normally shake hands.

“As a Muslim woman, part of practicing my faith means that I wear a hijab, and don’t shake hands with, or hug anyone of the opposite sex,” Hana Jafar wrote at Medium last year.

But the Danish Parliament on Thursday passed legislation requiring that all immigrants shake hands with the official conducting naturalization ceremonies. Failing to do so would demonstrate that the immigrant has not fully integrated into Danish society.

“If you arrive in Denmark, where it’s custom to shake hands when you greet, if you don’t do it it’s disrespectful,” Martin Henriksen, a lawmaker who has been critical of Islam and Danish People’s Party’s spokesman on immigration, told the New York Times. “If one can’t do something that simple and straightforward, there’s no reason to become a Danish citizen.” He hopes the law, which goes into effect January 1, will be followed by a ban on Muslim women wearing veils at citizenship ceremonies.

But several Danish mayors—typically the ones who officiate at the ceremonies—criticized the new law, which also forbids wearing gloves, as “purely symbolic” and irrelevant to an applicant’s qualifications. “They say the Danish Parliament, which approved the measure, has artificially elevated a social custom to a national value,” the Times said.

“It’s against my ideology and conviction to have to force other people to have body contact,” Thomas Andresen, the mayor of Aabenraa, told the Times.

Mogens Jespersen, the mayor of Mariagerfjord, told the national broadcaster that he would disregard the law and accept a nod or a bow from an applicant refusing to extend her hand, according to the newspaper, which continued:

One mayor said he had met a female asylum seeker who declined to shake his hand for religious reasons, but he did not find it disturbing. “I was in no doubt that she meant to show the exact same respect in her way as I did in mine,” said Soren Steen Andersen, mayor of Assens, on Funen Island, just off the Danish mainland.

The issue has arisen elsewhere in Europe in recent years. In August, a Swedish Muslim woman won compensation after her job interview was ended when she refused a handshake, the BBC reported. Instead of shaking the hand of her male interviewer, Farah Alhajeh, 24, placed her hand over her heart as an alternate sign of greeting.