The correct answer to this open question is the following.
One can find a list of powers forbidden to Congress in Article I, Section 9.
In this part, the Constitution prohibits Congress the legislation in the following areas: the Writ of Habeas Corpus, Bills of Attainder and Ex Post Facto Laws, the Port Preference Clause and Export taxes. The Constitution also prohibits Congress to grant titles of nobility to people and does not authorize public officials from accepting a gift or title from other Congress unless it is approved by Congress.