In Europe, is it legal to have a fully consentual open marriage? (specifically sexual relationships with other couples)

Question

As per the title : In Europe, is it legal to have a fully consentual open marriage? (specifically sexual relationships with other couples)

The question comes from the legal basis that in theory consentual choices are legal but sex outside of marriage may be not.

I know in the US there is such a thing like open marriage but in Europe (I'm not referring exclusively to UK, but Italy for example) the definition is blurred or non-existant. Take for example the case that someone thinks so strongly this is wrong, can they legally do any harm?

Answer 1

According to the Wikipedia article on Adultery

Adultery is no longer a crime in any European country. Among the last Western European countries to repeal their laws were Italy (1969), Malta (1973), Luxembourg (1974), France (1975), Spain (1978), Portugal (1982), Greece (1983), Belgium (1987), Switzerland (1989), and Austria (1997)

The article goes on to list various countries that used to regard it as a crime, and when and how those laws changed. Elsewhere in the article, various non-European countries that regard adultery as a crime are listed.

Similar information is include in an article from The Week "Where is adultery is still illegal?", which says:

The last European nations to decriminalise infidelity were Austria, in 1997, and Romania, in 2006.

The Wikipedia article on Fornication does not list any European country that has current laws against sex between people not married to each other.

It would seem that having an open marriage, or engaging in extramarital sex, is not illegal anywhere in Europe. In some other countries it would be technically illegal but enforcement would be unlikely, while in yet others the risk of enforcement would be significant.

Answer 2

In the UK at least, this isn't breaking any laws (and I doubt it would be anywhere else in Europe).

If you work for a religious organisation which prohibits this behaviour then you can be fired, and I think the UK armed forces take a pretty dim view as well, especially if an extra-marital partner is also serving. However outside of those exceptions this comes under the right to a private life.