Is it permissible for a Shafi'i to marry a Hanafi woman without her guardian, given the difference between the two madhhabs regarding the requirement of a guardian?

The majority of scholars hold the view that a woman's marriage is not valid without the consent of her guardian, in contrast to Abu Hanifa, who permits her to marry herself. The preponderant opinion is that of the majority. If a man believes that marriage without a guardian is invalid, then he is not permitted to contract marriage with a woman except with the permission of her guardian, because he would be undertaking something that he believes is forbidden and invalid. Thus, a man is bound by what he deems preponderant. Even if one party believes something to be permissible and the other considers it forbidden, the one who deems it permissible is not allowed to assist the other in performing what is forbidden. This indicates that whoever believes something to be forbidden is more obliged to refrain, as they would be committing what they believe to be a sin.