When we are in Christ we are also in the Spirit. Flesh is not a moral condition in Paul's thinking but a pre Christ relationship to life. Now Christians live out a new life, which is a relationship with Jesus. Here is a quote from a NT scholar and devout Christian who is the head of a Bible college.
All sin, Paul believed, is an individual's choice to break faith with God by inverting the Creator-creature relationship (Rom 1:18-32). Paul uniquely located the problem within a person's pretension to autonomy and the subsequent rupture in relationship. … God justifies the sinner and cancels his identity in Adam for a new identity in Christ. So flesh and spirit do not indicate philosophical or moral categories for Paul, but alternate identities in relationship. According to Paul one who is in Christ is correspondingly in the Spirit and a slave of righteousness. This is a given. He or she is not in the flesh (Rom 8:9). The reverse holds for those in Adam - they are in the flesh and slaves to sin and death.
His footnote to 8:9 amplifies his argument.
"Throughout Romans 6-8, the NIV persistently renders sarx as "sinful nature" and frequently supplies the phrase "controlled by" for ‘en’ and ‘kala’. It thus gives the impression that Paul says believers have two natures: a fleshly nature and a spiritual nature. This is particularly irritating and misleading in 8:9, where Paul simply says, "However, you are not in the flesh but in the spirit, if the Spirit of God lives with you" (my translation). The NIV has "You, however, are controlled not by the sinful nature but by the Spirit, if the Spirit of God lives in you."
"Once again, in Romans 6:20, the NIV unhelpfully supplies "the control of," thus tilting the meaning toward cohabiting moral natures and away from the contrast Paul is making between identities based on Adam or Christ.
John
NZ