Answered by Shaykh Rami Nsour
Question: In the Maliki school, what is the opinion regarding wearing pig skin? Do prayers need to be repeated when somebody’s foot has come into direct contact with pig skin contained in a shoe?
Answer: In the Maliki school, pig skin is considered impure even if it has been tanned. If a person has pigskin clothing on while praying or they move an item that is pigskin while in prayer, then the prayer is invalid and must be repeated. Your foot would not become impure by coming into contact with the pigskin unless some part of the leather was rubbed onto your foot.
One thing to point out it that it is not permissible to wear or use pig-skin like a wallet, belt, shoe insole, briefcase or jacket. The prohibition of use of pig-skin is in addition to the prohibition of buying or selling it. [Ahmed al-Dardir, Sharh al-Kabir]