Is working secretly as a painter on Saturdays and Sundays, which is against French law, permissible (halal) or forbidden (haram) according to Islamic law?

A Muslim must respect the laws of the country he has entered, as long as they do not violate Sharia, because Allah Almighty says: "O you who have believed, fulfill [all] contracts," and the Prophet, peace and blessings be upon him, said: "Muslims are bound by their conditions." Muslims should be a role model in fulfilling covenants and trusts, as Allah Almighty says: "And those who are to their trusts and their promises attentive," and He says: "And fulfill the covenant of Allah when you have covenanted." Therefore, if the law requires the worker to inform the authorities about his work on holidays or prohibits him from working on them, then this must be fulfilled.