Acts 15 is not vague. It is clear. Gentile believers were not under the Law. Peter, Paul and the other Apostles stated that this message was from the Holy Spirit and from them.
You can take Acts 15 to justify anything. ("Well, the old law no longer applies and the Apostles never said you can't kill somebody, so it's all good, as long as you believe that you're "saved".). /s)