Soft law = a quasi-legal instrument between hard-law and non-law, usually found in international law. In contrast with hard law which gives international actors binding responsibilities, soft law does not have any legally binding force. It is often used in frequently changing situations, when revisions are frequently needed or when states don`t want to commit to something solid, but are indicating a willingness to remain receptive to the possibilities for a certain topic.
Hard law = The differences between soft and hard law refer to obligations, precision and delegation. Thus, hard laws have a higher degree of legal obligation and precision, being written with different details and in several languages. Soft laws have a weak or no legal obligation among the parties and the terms used are vague, general and abstract. Regarding the delegation, soft law can usually be interpreted by the parties, while hard law delegates the interpretation or the enforcement to a third party, such as an international tribunal.
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http://law.wisc.edu/facstaff/trubek/hybriditypaperapril2005.pdf - Trubek D. M., Cottrell P., Nance M., 2005, Soft law, hard law and European integration: toward a theory of hybridity, University of Wisconsin [English]
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