Without knowing the details, one cannot give a certain answer. But, having
done business and used lawyers in both the U.S. and Brazil, I can tell you
that this should not be that complicated. The Governer's counsel would retain
your firm and you provide services for them in Brazil. Payments to you would
be subject to Brazilian Federal taxes. I am sure that the Governor's office
has done this before so they should be able to guide you, or seek counsel in
the capital city of the relevant state.

If your law firm is based in Brazil, I suggest you contact your local government for their laws and regulations. The information found at Business.gov pertains to US businesses and foreign businesses that do businesses in the US.