With all due respect to the current discussions in this thread, I'd like to go back to the original post: I've never considered the law of God to be different from the law of Moses. There are lots of reasons for this, but I will try to be brief and so I can't cover them all in one post.
1. I have not seen any verse that clearly says, "the law of God is the 10 commandments and the law of Moses is everything else". In fact, they are either used interchangably and at times what should be called the Law of God contains laws outside the 10 Commandments (and somewhat vise versa).
2. Interestingly enough, the phrase, "Law of God" is not used that often: only 7 times in the entire KJV. Perhaps more in other versions; I don't know.
The phrase is used in Josh 24:26, Neh 8:8, 8:18 10:28, Rom 7:22, 7:25 and 8:7. None of them reference the 10 comnandments although in Neh 8 it is speaking against Israels use of idols. Furthermore, if you look at Neh 10:28-29 and the following verses, you see them (down to verse 37) you see a long list of things of "God's Law" that they did that are beyond the 10 commandments (yet it is referred to as God's law).
3. "Law of the Lord" is mentioned 21 times, ahain not specifying the 10 commandments as a whole. I would like to hilight 3 of the 21: 1 Chr 16:40, 2 Chr 31:3 and Luke 2:23-24. All these verses include laws outside the 10 commandments. In fact, Luke 2:23 contains a reference to Exo 13:12 (which is before the law was given and later incorporated into the law).
3. 2 Cor 3. Reading the whole chapter, it would be hard to argue that the law spoken of here is not the 10 comnandments, yet it is called done away with, abolished and while neither called the law of God or Moses, it is attributed to Moses (v 15). I bring this up especially since I have read some say God's law was never abolished but Moses' law was.
The fact that its attributed to Moses is not a single incident. A few of the verses I've already given also attrubute "God's Law" to Moses.
5. This leads me to my final point: God didn't stop giving laws to Moses after Exo 20:17. Yes, the 10 commandments are special as God did write them with his own finger (not in front of the people, by the way) but the same God gave Moses many more in chapter 21 and beyond.
3 things should be realized: 1. Moses didn't come up with them on his own - not even under inspiration - but directly from God's mouth. 2. God gave them... 3. He gave them TO Moses.
These last three sub points make a strong case for all the 613 laws being God's since he gave them as well as Moses' since they were given TO him.
In conclusion... Yes, this are just some of the reasons. To me, its not a major thing since the covenent of grace is in effect.