Depends on what you consider "stolen". In most cases, the manga that is available is translated and edited by fans to make it accessible to English-speakers when the IP owners do not see a reason to do it themselves. The amount of manga that actually get official English releases is very tiny and western licensing companies do not have many incentives to start picking up obscure manga that no one without the ability to read Japanese have heard of. They're much better off going after manga that have already been made popular by fan-translated manga, or have some other property that has caught traction (for example manga with an anime adaptation that has official or unofficial subtitles).
Scanlations are often viewed by fans as the only way to read comics that have not been licensed for release in their area. However, according to international copyright law, such as the Berne Convention, scanlations are illegal. [1]
This is a snippet about the Berne Convention:
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. The Berne Convention has 179 contracting parties, most of which are parties to the Paris Act of 1971.
The Berne Convention formally mandated several aspects of modern copyright law; it introduced the concept that a copyright exists the moment a work is "fixed", rather than requiring registration. It also enforces a requirement that countries recognize copyrights held by the citizens of all other parties to the convention. [2]
