In a complex case, Tony Wright, of the Exmoor Foxhounds, was first found guilty of hunting a wild animal with dogs after a £65,000 private prosecution was brought by the League Against Cruel Sports in 2006.
But Mr Wright, from Simonsbath, maintained he had worked hard to stay within the Hunting Ban, using two hounds to flush out a fox for shooting, in April 2005.
It was just weeks after the Hunting Act came into force in February 2005.
He was originally found guilty at Barnstaple Magistrates Court and fined £500 with £250 costs.
But in December 2007 the case was overturned in Exeter Crown Court.
The Crown Prosecution Service appealed that judgement, arguing that it should have been for Mr Wright to prove that he was hunting legally, and that "hunting a mammal" includes "searching" for it. The High Court today rejected that appeal.
Mr Wright said: "This prosecution has now dragged on for over three years and during that time I have been living under the threat of a criminal conviction.
"If this judgement, though, makes it less likely that other people will face the sort of vindictive prosecution that I have been through then it has all been worth it."
Simon Hart, chief executive of the Countryside Alliance, said: "Even before today's judgement, only five people connected to hunts have been convicted of any offence since the Act came into force.
"The CPS argued in court that if it lost this appeal prosecutions under the 2004 Act would rarely be viable so there should now be even fewer prosecutions.
"The Hunting Act is an increasingly pointless piece of legislation that offered little and has achieved less.
"Politicians of all parties are coming to realise that it has failed and it is now a question of when, not if, the Hunting Act is repealed."