Really, this is a quite simple issue. The OT contains three sets of rules: Moral, Civil, and Ceremonial; care must be taken to distinguish in applying. The Civil and Ceremonial laws are not applicable to those living outside of OT Israel. This includes the civil application, such as punishment, of the moral infractions. The moral law still applies. Thus, practicing witchcraft is immoral, but may not (as in might not) be punished by the civil authorities.
I like the way the Book of Common Prayer expresses it in Article VII (in relevant part):
Although the Law given from God by Moses, as touching Ceremonies and Rites, do not bind Christian men, nor the Civil precepts thereof ought of necessity to be received in any commonwealth; yet notwithstanding, no Christian man whatsoever is free from the obedience of the Commandments which are called Moral.
Related to the Death Penalty...
It should be noted that there are those who believe that the Noahic covenant or commandment, see Gen. 9, mandates the death penalty for murder. This is not a command limited to Israel, but is a commandment for the whole human race.
Specifically, Gen. 9:5-6 provides
 And for your lifeblood I will surely demand an accounting. I will demand an accounting from every animal. And from each man, too, I will demand an accounting for the life of his fellow man.At issue, really is whether this passage is prescriptive or predictive. I believe that it does not require the exercise of the death penalty, rather it recognizes that killing brings more killing. I believe the Lord is warning us of the consequences of killing.
 "Whoever sheds the blood of man,
by man shall his blood be shed;
for in the image of God
has God made man.
(Note too, the chiastic structure of Genesis 9:6.)