There are multiple definitions - click on the translation that matches your context.

actio pro socio

Substantiv

partial

shareholder derivative lawsuit

Comparative law notes

Switzerland

Although the traditional German definition of this phrase - in the narrower sense - is an action BETWEEN the owners (see below), we hesitate to line this English phrase up as a full match. However, the German phrase actio pro socio has come to express the notion that certain shareholders can and will bring a legal action on behalf of the company (i.e., enforcing claims to which the company is entitled) against outside persons with no ownership interest, which is actually what a "shareholder derivative suit" is.