A spokesman for the FIA said the matter was "under active consideration".
He said the FIA was a non-political organisation and was considering if Hamilton's T-shirt broke its statutes.
It was not immediately clear which statute from governing body the FIA was at issue.
Asked whether the FIA considered the T-shirt to be bearing a political message, the spokesman said: "That's the consideration we are looking into."
The only reference to politics in the statutes is a requirement on the FIA to "refrain from manifesting discrimination on account of race, skin colour, gender, sexual orientation, ethnic or social origin, language, religion, philosophical or political opinion, family situation or disability in the course of its activities".
The sporting code forbids competitors from "affixing to their automobiles advertising that is political or religious in nature or that is prejudicial to the interests of the FIA".