Your memo is trumping a Congressional statute. You don't have the discretion on whether to follow the law or not.
You know, in the oath that brand-new citizens take, it contains six different references to 'the law.' If it's good enough for us to ask brand-new citizens to affirm their devotion to the law, is it too much to ask that the president do the same?
No law can give Congress a backbone if it refuses to stand off as the coequal branch the Constitution made it.
If you can turn off certain categories of law, do you not also have the power to turn off all categories of law?
If a president can change some laws, can he change ALL laws? Can he change election laws? Can he change discrimination laws? Are there any laws, under your theory, that he actually HAS to enforce?