In most countries in Europe, and even worldwide, knife throwing is perfectly legal.
Of course, many countries have rules about carrying knives in public, and transporting them, but those rules are so open to language interpretation that it's best to use local sources to learn about them.
A good collection of international weapon laws on knives is maintained at Wikipedia.
However, there are some countries where EuroThrowers members have reported restrictions on knife throwing. The throwing itself is not banned, but sometimes throwing knives are illegal. People throwing in those countries use ordinary (but blunted) knives for their sport.
A EuroThrowers member succeeded in having the ban on knife throwing lifted. You now can obtain permission to throw knives in private and in public.
A member reports that throwing knives are legal as of 2003!
Throwing knives are illegal. Details see Gesetzliches zu Wurfmessern in der Schweiz.
The Schweizer Werfer Vereinigung had some success in legalising their throwing knives!
Importing throwing knives requires a police permit (according to the customs). If throwing knives are then legal seems to vary depending on the jurisdiction region within Australia.
Throwing knives are illegal.
Throwing knives are illegal. (Article 3, §1 of the 2006 Weapons Act)
Throwing knives are illegal. (Loi du 15 mars 1983 sur les armes et munitions", §1 c)