The @PicketLink qualifier annotation currently only has the following ElementType targets:

@Target({ElementType.TYPE, ElementType.FIELD, ElementType.METHOD})

It should also include at least PARAMETER, since that's one more place where a CDI qualifier can be used.

One possible use case: when producing an EntityManager, as the reference suggests:

@Produces
@PicketLink
@PersistenceContext
private EntityManager picketLinkEntityManager(unitName = "picketlink");

it is common practice to include a disposer, but it's currently not possible due to this issue:

public void dispose(@Disposes @PicketLink EntityManager entityManager) {
    if (entityManager.isOpen()) {
        entityManager.close();
    }
}