According to Wikipedia, Holocaust denial is against the law in 14 European countries: https://en.wikipedia.org/wiki/Laws_against_Holocaust_denial
In this recent news story, Deborah Lipstadt explains why Holocaust denial should not be against the law: http://forward.com/the-assimilator/333780/deborah-lipstadt-explains-why-holocaust-denial-shouldnt-be-a-crime/?attribution=blog-article-related-1-headline
The following quote is from the news article, cited above:
Famous Holocaust historian Deborah Lipstadt opposed criminalization of Holocaust denial in a debate at the Oxford Union Society last month, which is shown in the video below. Even after years of fighting a libel suit filed against her in 1996 by Holocaust denier David Irving, Lipstadt says she is not in favor of laws against Holocaust denial.
“I support this motion Mr. President, because I am convinced that freedom of speech means nothing unless it includes the freedom for offensive people to be offensive,” she says. “We who are offended by them, must accept that, as a cost of living in a free society.”
In the video, she details her strong opinions on freedom of speech and why Holocaust criminalization will not benefit the cause against Holocaust deniers.
Now that I have permission from Deborah Lipstadt, I will continue to deny the Holocaust.
The name Lipstadt is the name of the town in Germany, from which Deborah’s ancestors came. My German ancestors came from a town in Germany that was only a few miles from the town of Lipstadt, but Deborah and I are world’s apart in our thinking.
I have met David Irving twice and have heard him speak on each occasion. Sadly, Irving is now only a shadow of his former self, and can no longer defend himself against people like Deborah Lipstadt.