This book is about how sustainability criteria may be used in a legal framework, with the purpose to promote and safeguard sustainable products and their production. The research and analysis in the book are conducted on the basis of the EU approach to use sustainability criteria for biofuels in the transport sector, legally expressed in Directive 2009/28/EC, and its amendments in Directive 2015/1513. The book is presented in the form of a licentiate thesis by compilation. It includes five independently written and published in international journals papers, which deal with different aspects of the researched problem, and the "main body" of an analytical and summarizing character.