The Work Cooperative Social Security Contribution

Upon the enactment of Law 9876/99, of November 26, 1999, a part of the system of social contribution payable by companies was modified, and one of the contributions payable by companies was fixed at 15% of the invoice for services rendered by work cooperatives:

"Art. 22. The contribution payable by the company, earmarked to the Social Security, in addition to provisions in art. 23, corresponds to: (...)
IV – fifteen percent of the gross amount of the bill of services [nota fiscal] or invoice for services rendered to the company by the members of the work cooperatives."

However, it seems that the requirement for the engaging companies to pay a 15% contribution on the invoices for services from work cooperatives is totally unconstitutional, to the extent that: