It is a shame that in 2024, 35 years after Richard Stallman created the GPL, there is no EU or USA or international treaties taking in account copyleft licenses rights.

If a company A violates the GPL license, using the source code of a product P in a closed source product, then only the original authors of the product P can sue the company A, and only for the parts for which they own the copyrights.

Users of P and normal citizens cannot sue A. They have no "rights" to defend.