Let's take gay people as an example. Moses said no, Jesus said it's all about love, and Paul said no to gay people. So even though Jesus is always right, in practice he was usually pretty vague, so Paul ends up with the overrule.
*Side note: some people believe that Paul and/or Moses were only referring to gay people in the context of pagan ritual sex, and that Jesus's "love" should take priority. I'd believe Moses was about pagan sex and Paul is non-canon if I were still Christian. This shows that there's plenty of room for interpretation. The previous paragraphs are simply the evangelical mainstream interpretation.
Edit: A cynical me would also say that interpretation depends on agenda.