All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
If you are sure that he practices magic, you must advise him and remind him of Allaah the Almighty and that he is facing great danger due to this grave sin in the Hereafter as well as in this worldly life. If he does not repent, you must forsake him and protect yourselves with Sharee'ah sanctioned supplications. If you can raise his case with the authorities to deter and punish him without (you) being harmed, then do so.
Allaah Knows best.