Yes how is that nailed to the cross those two tablets of stone? You can't nail stone to a cross.
If He blotted out His own law then He can't condemn the unrepentant mocker and murderer next to Him on the cross. If that law is now gone then what is testifying against that man that he's a sinner? Where's the rules to judge him with?
The law is still here. If I open my Bible I can still read it. It isn't blotted out. Maybe the tablets of stone are even still in the Ark somewhere.
After Jesus died the law of sin and death was still in Paul's flesh.
The law is spiritual, you can't just kill that.
Romans 8
For we know that the law is spiritual, but I am carnal, sold under sin.
For I delight in the law of God according to the inward man. 23 But I see another law in my members, warring against the law of my mind, and bringing me into captivity to the law of sin which is in my members.
That law of sin and death in his members sounds more like a rule, a natural law: I have to sin, I can't obey God. Flesh can't please God.
I think here's that written thing testifying against us that had to be blotted out:
And I saw the dead, great and small, standing before the throne, and books were opened. Then another book was opened, which is the book of life. And the dead were judged by what was written in the books, according to what they had done.