It is confirmed that the Prophet , prohibited us from wearing form fitting clothes or shoes [while in the state of Ihraam (ritual consecration)], and the scholars established that if the shoes cover the toes or the heel, then they are form fitting shoes even if they do not cover the upper part of the foot. Ibn Hajar extensively elaborated on this matter and then said, “To conclude, it is absolutely permissible to wear shoes that expose both the heel and the toes, as in this case they are exactly like slippers. However, it is not permissible to wear shoes which cover either the toes, or the heel, unless one cannot find the other type of shoes which expose the toes and the heel. In case a person wears what is forbidden for a necessity and then finds what is permissible to wear, then he is obliged to immediately take them off [the shoes that are forbidden to wear] otherwise he is sinful and he is obliged to offer a sacrifice."

Allaah Knows best.