Romans 6:15 refutes 119's interpretation of Romans 6:14 by context

Romans 6:15 says "What then? Are we to sin because we are not under the law but under grace? By no means!" Paul anticipates a misunderstanding of v.14. If "under the law" in v.14 merely meant "under the power of sin," there would be no reason for anyone to misunderstand and think it now permits sinning. The objection only makes sense if "the law" = Law of Moses — removing that restraint might appear to open the door to sin.