Of course, that doesn't mean Avengers haven't broken the rules. Some members of the team have habitually broken the rules, which has caused a lot of problems for the team over the years.
Scarlet Witch found redemption with the Avengers, like her brother, but she also had more problems than Quicksilver did. Scarlet Witch's powers and her descent into villainy led to her fighting the team several times. She ended up killing several members, which led to her and Quicksilver creating the House of M reality when the Avengers and X-Men were making plans to deal with her.
Scarlet Witch depowered the mutant race at the end of that affair, although she did resurrect Hawkeye. Since then, she's had few problems with the team, although she did play a role in the Apocalypse Twins' plot mostly against her will.