Some one asked the other day, ‘Can a person be saved living a life of sin?’
Possibly two things they could have meant by this: Is a sinful person ever able to be saved? or, is one who is saved ever going to sin again and are they in danger of loosing their salvation? For the first one, most definitely. Otherwise, none of us would have a chance, for we are all sinners.

“Why it is necessary that we be able to choose evil for us to have free will, while it is not necessary that God be able to choose evil for Him to have free will?” was the actual question.
For starters, I must admit my limits and refer my readers (all one of me) to Lewis or Augustine, Bonhoeffer or Athanasius for a detailed answer. Dr. Craig is certainly well thought out, but I always like to think things through myself.

Short answer: Good is defined by who God is, His very nature. Evil is turning from or disobeying God, and as we are like but separate entities, we have that choice. A choice that God does not have. God cannot turn from Himself, though He may do as He pleases.

“for all have sinned and fall short of the glory of God,”(Romans 3:23Romans 3:23English: Contemporary English Version (1999) – CEV23 All of us have sinned and fallen short of God’s glory.WP-Bible plugin) “For the wages of sin is death, but the gift of God is eternal life in Christ Jesus our Lord.” (Romans 6:23Romans 6:23English: Contemporary English Version (1999) [...]

“Make sure you floss regularly and brush your teeth after every meal.”Floss

That was a rule in my parent’s house that I heard every day growing up. Before bed, “Did you brush your teeth?”
“Yes.”
“Tonight?”
“… no.”

There was no real discussion; it had to be done in our house as I am sure it was so in others.
My own daughter denies it as vehemently now as I once did (and sometimes still do when my wife asks). “Brush your teeth” is not a rule for the discomfort and anguish that children imagine, but to instill in us the good habit of keeping our teeth clean; one that responds to the natural inclination of teeth rotting and falling out.

The same may be said for the Law of Moses. God’s Law is not intended as the Ultimate Party-pooper, but simply a check to the fallen nature of Man; Laws that show us the reality of the world around us, meant to protect us from our teeth falling out: to keep us from harms way.