Is he who believes it permissible to look at the face and hands of a non-mahram woman, and acts upon that belief, sinful; and is that considered making the forbidden permissible?

The statement that the face and hands are not 'awrah (parts of the body that must be covered) and thus do not need to be covered, and that looking at them is not forbidden as long as there is no suspicion (of lustful intent), has been adopted by many scholars, such as the Hanafis and Malikis. Whoever adheres to this view through imitation (taqleed) is not sinful. Such a person is not considered to be deeming lawful what Allah has forbidden, nor does he exit the fold of Islam, because he has fulfilled his obligation due to his ignorance, and he must imitate a scholar in matters he is ignorant of.