Paul speaks of people sinning as if sin were their master or king that controlled them. Alternate translation: "Do not let sinful desires control you" (See: [[rc://en/ta/man/translate/figs-personification]])
Obeying the mortal body's lusts would be the result of letting sin rule in the body. That is why Paul commands people not to let sin rule in their mortal body—so they they do not obey its lusts. Paul speaks of people doing the evil things they desire as if the body had evil desires and commanded people to do what it desires. (See: [[rc://en/ta/man/translate/figs-personification]])