This is a simple answer, they can do whatever they want to do. As Christians, we understand the ten commandments to be God’s established law that is fully moral and most of our laws can easily point back to it. (Anyone that says the Sharia law is moral, does not fully understand it.) If we want to understand what Christians can and cannot do, we must understand what they are allowed to do.
Christians that have been washed, sanctified, and justified in Christ know that all things (besides what God considers sin) are lawful to them. This means we can do whatever we want. The question now is not a can but a should. Should we do this or that? Some believe it’s okay to watch movies while others believe it is sin. However, if I watched movies all day and did not do anything but watch movies every day of the week for three months, what did it do for me? A job would be lost, finances would lose, and I would not have accomplished anything useful. Now if I limited myself to the number of movies I watched, I would have a better chance of it being alright to do.
1 Corinthians 6:11-12
11And such were some of you: but ye are washed, but ye are sanctified, but ye are justified in the name of the Lord Jesus, and by the Spirit of our God.
12All things are lawful unto me, but all things are not expedient: all things are lawful for me, but I will not be brought under the power of any.
Now that we’ve gone over what we can and cannot do (we can do pretty much whatever we want), let’s go over what being a Christian really is. A Christian is someone that came to Christ and may have killed, but now helps to prevent others from making the same choice. Or perhaps he used to steal, now he gives to others in need. Whatever the ill deed of the past creature was, a Christian is a new creature in Christ and ought to show it. While we may fall, we need to get back up and glorify God. Remember these scriptures and suffer for Him. We are not ashamed.
1 Peter 4:15-16King James Version (KJV)
15 But let none of you suffer as a murderer, or as a thief, or as an evildoer, or as a busybody in other men’s matters.
16 Yet if any man suffer as a Christian, let him not be ashamed; but let him glorify God on this behalf.