Acharei Mot - R'vi'i
Where to Sacrifice (and to Whom)
G-d gave Moshe further instructions for Aharon, the kohanim and the people in general: it is stringently forbidden to offer a sacrifice other than in the Temple or Tabernacle. To do so is like just murdering an animal for no reason. Such sacrifices carry the penalty of kareis (spiritual excision). Peace offerings are desirable to G-d only when offered in the proper place, through a designated kohein. (Throughout the Book of Kings we see that such-and-such king was good but he failed to abolish the private altars people used. Here's where such altars, called bamos, are forbidden.)
It should go without saying that offering a sacrifice to anyone or anything other than G-d is right out. The Torah stresses these points now so that people will not misconstrue that the goat sent "to Azazel" was a sacrifice outside of the sanctuary or - G-d forbid! - to another power. (See Baal HaTurim on 17:3.)