In the early days of the newly emerging Libertarian Philosophical Movement and the formation of the Libertarian Party, there was a fringe group of Libertarians who called for the decriminalization of bestiality. These activists were present at a Libertarian Conference held in New York City in 1969 and around that time, Murray Rothbard claimed a Neo-Randian group called Students of Objectivism for Rational Bestiality existed in the outer reaches of the libertarian movement. These so-called Bestiality Boys promoted what they called Rational Bestiality. Their contention, as I understand it, was that "bestiality is illegal because humans are irrational animals and that, if humans were rational, citizens would not be arrested and jailed for engaging in sexual acts with the animals they own."
While those calling for the decriminalization of bestiality have always been present in the Libertarian Party, this issue was elevated to a whole new level when in 2011 and 2012, two Libertarian Party Presidential Candidates and one Presidential Candidate of the Boston Tea Party, made statements in favor of decriminalizing bestiality.
Carl Person, who was seeking the Libertarian Party's Presidential nomination, was the first to re-address this issue when he wrote:
The victimless crimes are prostitution, bestiality, sodomy, drugs, abortion, and the principles are that we shouldn't be regulating what people do to themselves, and the cost of the regulation should be saved and returned to taxpayers, to reduce taxes, and enable the economy to grow with commerce instead of with prisoners, private jails and private jail guards.
When asked for a clarification with respect to his position in support of legalizing bestiality, Carl Person provided the following statement regarding this issue:
When I mentioned "bestiality", I was referring to animals, not humans (Note: some statutes prohibiting bestiality include children within the definition.). Bestiality as a victimless crime would center on two elements: 1. "property rights" - limiting the practice to one's own animals or with wild animals (not owned by anyone) and 2. "consent" and/or "non-injury" - if the animal is willing and is not injured in the process. If the animal is already dead, the victimless crime would become a variant of necromancy, and have to be analyzed in a similar fashion. I'm not a practitioner or advocate of bestiality and am only trying to apply Libertarian principles to a seldom discussed victimless crime.
http://drtomstevens.blogspot.com/2013/06/support-for-decriminalization-of.html
Several more of other groups trying to legalize it too.