But WHO gave law in Gen 2:17 ? Take care WHAT is LAW in 2:17. It is not stupid law. This law states: do not eat fruit from tree of KNOWLEDGE OF GOOD AND EVIL : which I think means do not follow any other law (except this). So this law is what you say: follow GRACE. Banning the LAW is also a LAW. Please think of it. This is paradox but you can not escape it.
My starting pint is that Eden had to be different place that we think. Could the leg be broken there ? Braking the leg is also reulting from law (physical one). So maybe in Eden there really was no any law, except not discovering law ?
Remember that Adam was created on similiarity and image of God. So he could be powerful being. If he wanted to dicover laws maybe he was able to create them.