I am not trying to be cute, but I think that they are both in effect. The fact that we continue on each day with so much sin in our lives and in this world, proves to me that grace is in effect.
The fact that our consciences alert us, when we sin, proves that the law still exists.
However, I think that the definition of "the Law" is best defined as the 'teaching and instruction of God.'
One does not gain salvation by keeping to God's teaching and instructions, but neither is that a good reason to ignore them, as if they were all for a different people, time, or place! The commandments are for anyone who is a child of God. They bring life, and not death. They are for are good and not for our harm.
One can not be harmed by tithing, unless one sees it as a part of keeping all the "Law" unto salvation. Then the "law" becomes a curse.
If the New Covenant is a covenant of grace, and it is, then what does it mean when He states that He will write the "Law" on our hearts? Jeremiah 31-31thru34