Some Muslim and Jewish groups prohibit or discourage touching members of the opposite sex outside the immediate family.

Ilvy Njiokiktjien for The New York Times
By Martin Selsoe Sorensen
Dec. 20, 2018

COPENHAGEN — Denmark will require anyone who takes Danish citizenship to shake hands at the naturalization ceremony, under a law passed on Thursday, which lawmakers say is aimed at Muslims who refuse on religious grounds to touch members of the opposite sex.
The law has prompted strong reactions from some of the mayors who must conduct such ceremonies, and who are upset that they will become the faces and fists of a policy they call awkward, “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.

But Denmark is not alone. Authorities in Switzerland and France have recently cited “lack of assimilation” in rejection of citizenship to foreigners who refuse to shake hands with officials.

“If you arrive in Denmark, where it’s custom to shake hands when you greet, if you don’t do it it’s disrespectful,” said Martin Henriksen, a lawmaker who has been critical of Islam and is the right-wing Danish People’s Party’s spokesman on immigration. “If one can’t do something that simple and straightforward, there’s no reason to become a Danish citizen.”

source:

https://www.nytimes.com/2018/12/20/world/europe/denmark-muslims-handshake-law.html