Which agreement do most countries use as the basis for their copyright laws?

Copyright is a creation of law in each country, and therefore there is no such thing as an international copyright law. Nevertheless, nearly 180 countries have ratified a treaty – the Berne Convention, administered by the World Intellectual Property Organization – that sets a minimum set of standards for the protection of the rights of the creators of copyrighted works around the world.

In addition, there have been efforts to harmonize copyright law in Europe and other regions. The differences in national copyright laws, however, can represent a challenge for global organizations with employees working in different countries and sharing content across boundaries.

Berne

Explanation:

The Berne Convention for the Protection of Literary and Artistic Works, usually known as the Berne Convention, is an international agreement governing copyright, which was first accepted in Berne, Switzerland, in 1886.