User blog comment:EmpyreanSmoke/Supernatural Q&A/@comment-27006668-20151025184716/@comment-24834479-20151025193549

1. Angels were made so that hey physically couldn't enter a body without permission.

2. Yes, he could change the rule.

3. He was too strong to be expelled.

4. I used to believe they were equal in terms of power, but not I'm not sure that a regular blade could kill an archangel.