Japan's Prime Minister Shinzo Abe has said it was a "dangerous act".
They had been held on suspicion of manslaughter and an offence under the Dangerous Dogs Act.
The Dangerous Dogs Act 1991 has long been one of the most controversial pieces of legislation on the statute book.
Mr Swankie, 52, from Peterhead, pleaded guilty at an earlier hearing to a breach of the Dangerous Dogs Act after accepting that Woofie was "dangerously out of control in a public place".
The 1991 Dangerous Dogs Act was introduced after a spate of vicious attacks on young children and is designed to make it almost impossible to own a Pitbull without complying with strict regulations.
In the UK, the breeding, sale or exchange of pit bull terriers is banned under the Dangerous Dogs Act 1991 and people who already own pit bulls must keep them muzzled and on a lead in public.
The dog was seized by police last week after a warrant was issued by Truro Magistrates' Court under the Dangerous Dogs Act to determine whether it is a prohibited breed, or a pit-bull type which has restrictions against it.
The Dangerous Dogs Act 1991 means it is an offence to be the owner of a dog that is dangerously out of control in a public place but it does not apply to attacks that take place on private land.
It's possible when the Dangerous Wild Animals Act was passed in 1976, which made it illegal to own exotic but dangerous animals, a handful of owners released their pets into the wild.
But in 1976 the government introduced the Dangerous Wild Animals Act to protect the public and animals.
After the introduction of the Dangerous Wild Animals Act in 1976, many private collectors are thought to have turned their animals loose.
The creatures have strong front claws and will defend themselves if they feel threatened but a Dangerous Wild Animals Act licence is not needed to keep a one as a pet.
BBC: Ramblers spot coati on woodland walk in Buckinghamshire
Jane: If there is evidence of poor or dangerous workmanship Corgi do act.
He had accused the judge of failing to act impartially against dangerous criminals.
ECONOMIST: The political mood darkens in the tiny island state
When the crisis peaked in September of 2008, failure to act was the most dangerous threat to life as we know it.
FORBES: Roger Lowenstein Dismisses Charges Against Wall Street; Not So Fast
So far though the overall impression at this conference is that cyberspace is a frightening and dangerous place and we need to act together to do something about it.
Perhaps the most dangerous aspect of this "transition support act" is that it would commit the United States to a leadership position in the restoration of Syria, and is very vague about what that looks like.
Scientists believe the H1N1 virus epidemic is no more dangerous than seasonal flu, and schools should act accordingly, Sebelius said.
Meanwhile, the very act of spreading life on Mars has some dangerous unintended consequences.
Dame Suzi Leather, chairwoman of the HFEA, said they had received some complaints about treatment that might be dangerous or banned in the UK but had no powers to act.
While Apple has been slowly repairing the faulty directions provided by its mapping application, the company had to act quickly after learning that Australian motorists were being stranded in a dangerous environment.
IPPs were introduced under the 2003 Criminal Justice Act and aimed at offenders of a violent or sexual nature deemed to be dangerous to the public.
In the U.K., it says, the overall impact of the 1999 Immigration and Asylum Act and the 1999 Immigration Bill "proved detrimental to refugees, " while, "cruel and dangerous methods of restraint, including the deliberate blocking of breathing passages, " were the subject of inquiries in Switzerland and Belgium following deaths by asphyxiation during forcible deportation.
应用推荐