Why is the power of sin the law?
1cor15:56
The context is the post resurrection sinless state, where...
unto them that look for him shall he appear the second time without sin unto salvation. (Hebrews 9:28)
The context of 1 Cor 15:56 is the post resurrection sinless state, after the mortal earthly corruptible body has been laid to rest in the dust of the earth.
Why are sinfull passions aroused in people by the law if they live under it?
Rom7:5
But now we are delivered from the law, that being dead wherein we were held; that we should serve in newness of spirit,
Paul still advocates the Law of Sola Scripture, but applied in the newness of the spirit, the heart of flesh.
and not in the oldness of the letter. What shall we say then? Is the law sin? God forbid. Nay, I had not known sin, but by the law: for I had not known lust, except the law had said, Thou shalt not covet.
Paul states, that he followed the written law extrinsically as to be seen to abide by it, not understanding what its purpose was, because deep down he still lusted and never considered that the internal man is what counts to God.
Paul realised that under the letter of the law he was ignorant of the lusts of the heart and it was when he realised this, that he declared himself dead, because he realised he was condemning himself by virtue of his unclean heart through the very letter of the law that he upheld in high regard as a pharisee.
Paul died to his fleshly carnal ways that he defines as sin, because the lusts of the heart were never considered as part of the equation of sinning.
Rom 7:21 — Rom 7:22
I find then a law, that, when I would do good, evil is present with me.
For I delight in the law of God after the inward man: