Except for the Netherlands, where a national deposit collection has been built through voluntary deposit agreements between the national library (Koninklijke Bibliotheek) and the publishers, most countries rely on a legal instrument of some sort in order to ensure the comprehensiveness of their national deposit collection.

In many countries the measure requiring the legal deposit appears in a legal deposit act (France, Greece, Indonesia, Norway, Peru, South Africa, Sweden), while in other countries it is part of another act, such as the copyright act (Australia, Great Britain, United States), the national library act (Canada, Japan, Nigeria, Venezuela) or a general "libraries act" (Tasmania). In some jurisdictions, it takes the form of an administrative decree or ordinance (Chile, Cuba, Nigeria).

In all countries with a legal deposit system, published material, often described as library materials (books, periodicals, newspapers, microforms, sheet music, maps, brochures, pamphlets, etc.), constitutes the basis of the national deposit collection. But in many countries, audio-visual material (sound recordings, films, videos, etc.) is also subject to legal deposit (Canada, Finland, France, Germany, and South Africa). A few countries have already included electronic publications in their legislation, including Canada, Denmark, Finland, France, Japan, Norway and South Africa, among others, but they have done this in different ways. France and Japan, for example, have modified their legislation to include electronic publications, but have specifically excluded on-line electronic publications because of the numerous unsolved technical problems related to the acquisition and preservation of such material.

Whereas the national institution chosen to receive the deposit material is often the national library of the country (China, Estonia, France, Kuwait, Lithuania, United Kingdom), it could also be the parliamentary library (Israel, Japan, United States), the national archives (Antigua, Bahamas, Senegal), one of the main government libraries (Chad, Ghana, Hong Kong) or, in a few cases, one of the main university libraries (Liberia).

The development of a national deposit collection of published material in its broadest sense has to rely on a legislative foundation in order to ensure that all publishers will comply. Furthermore, to be taken seriously by depositors, the legislation has to be enforceable. While it is necessary to have legal deposit based in legal statute, it is much more desirable for publishers to be involved because they are convinced that it is ultimately to their own advantage to systematically send copies of their published material to a national institution which will record and preserve their production for future generations.

The law is the sum of all enforceable rules governing the relations of individuals among themselves (private law), the relations of the state with individuals (public law) and the relations of states among themselves (international law). The purpose of laws is to organize the political and social life of a society in order to ensure its orderly development. With the Constitution as the fundamental law of a country, the two main sources of law are Statute Law, which is made up of acts passed by the legislative body of the country, and Case Law, which is made up of a body of court decisions, mainly courts of appeal, which act as a guide for judges in deciding future cases. In countries with a civil law tradition, the law is codified, for example into a civil code, an intellectual property code, a labour code, etc., and these codes are the main source of law. In countries with a common law tradition, judicial decisions have to take into account the rule of precedent, which binds courts to follow precedent cases. An act is a form of written law, which formally expresses the will of the state on a specific matter, such as a legal deposit system. The most important aspect of a law is the fact that it is enforceable, and therefore the state can use its vested constitutional power to force the members of a society, individuals and organizations, to comply.

Legal deposit legislation serves a clear national public policy interest by ensuring the acquisition; the recording, the preservation and the availability of a nation's published heritage. Such a national collection is undoubtedly one of the major components of a country's cultural policy and should also be considered as the foundation of a national policy of freedom of expression and access to information. The role of a legal deposit system is to ensure the development of a national collection of published material in various formats. It should also support the compilation and the publication of a national bibliography in order to ensure bibliographic control over a comprehensive deposit collection. Finally, effective legal deposit legislation guarantees, to citizens and researchers within the country and abroad, access to a research collection of the country's published material. Bibliographic control and the accessibility of the national collection are also two international IFLA/UNESCO commitments, namely UBC (Universal Bibliographic Control)3 and UAP (Universal Availability of Publications),4 that all countries are invited to adhere to.

3. A long-term program for the development of a worldwide system for the control and exchange of bibliographic information.
4. A program by which a country ensures that at least one copy of everything it has published is preserved and can be made available through loan or copies to any scholar anywhere in the world who needs to consult it.