Are referendum results binding?

Costa Rica
Answer
Optional referendum - sometimes
Source
Political Constitution of Costa Rica (ConstituciónPolítica de la República de Costa Rica)
http://aceproject.org/ero-en/regions/americas/CR/costa-rica-constitucion-politica-de-la-republica
Comment
When satisfies the turnout requirements: 30% in thecase for law proposals and 40% for constitutional amendments.