"Paternity testing has been banned in France for the past 15 years and for French fathers to truly set their mind at ease, they would have had to secretively send samples to foreign paternity testing labs. If those samples were found in the post by officials on their way to foreign laboratories, the French men who sent them could theoretically face a year in prison and a 15,000 Euro fine. This year the ban was challenged but the French Government decided to uphold and maintain the anti-paternity testing law.
The reasons for which the Government said the ban should remain were related to the preservation of peace within French families. According to some online articles, Germany, has also banned (or plans to ban) paternity testing for similar reasons. French psychologists suggest that fatherhood is determined by society not by biology. For this reason, the President's wife Carla Bruni describes her father as the man 'from whom she takes her name'. She is friends with her biological dad too but she doesn't refer to him, or think of him as, her father." Source
This reminds me the Jewish law that rules that the children of married women are all kosher and presumed of her husband. I heard stories of rabbis purposefully confusing things and cheating to avoid declaring a child mamzer (bastard) although the husband had been dead for the last ten months.