(Devarim 12:17) "your cattle and your flocks": This refers to sin-offerings and guilt-offerings. What does Scripture come to tech us? If (that it is forbidden) to eat sin-offerings and guilt-offerings outside the wall, this can be derived a fortiori from ma'aser. If that (they may not) be eaten before their blood is sprinkled, this may be derived a fortiori from thank and peace-offerings (lower-order offerings).
If that a non-priest (may not eat of them) even after their blood had been sprinkled, this may be derived a fortiori from bechor, viz.: If bechor, a lower-order offering — if one eats of it (even) after its blood has been sprinkled, he transgresses a negative commandment, then sin and guilt-offerings, if one eats of them (even) after their blood has been sprinkled, how much more so does he transgress a negative commandment!
The purpose of the verse, then, must be to teach us that if one eats a sin or guilt-offering outside the curtains (of the tabernacle) he transgresses a negative commandment.