The Three Laws of SCRUM - My Humble (?) Opinion

I've been doing SCRUM for four years now. I've heard various ways of describing it, various rules and guidelines. It is my belief that there are many BKMs to SCRUM, but very few rules. And here they are:

    1. Short iterations. At the end of each such iteration the Product owner should be able to announce which new features had been added during that sprint.
    In order for the latter to happen, we probably need some sort of definition of done.
    2. Self managed team 1: team members - all team members - commit to the stories they takes upon themselves.
    This means all members commit to all stories - not only the stories they are the owners of.
    3. Self managed team 2: team members - all team members - take part in a meaningful retrospective which takes place at frequent intervals. At the end of each retrospective it is expected that the team will adapt their process based on what had been discussed.

everything else - daily stand up meetings, dashboard, tools, poker planning, velocity, actuals, length of the sprint, required level of quality delivered at the end of each sprint, definition of done, etc. etc. - are only BKMs and should be treated as such. It is my belief that if a team maintains the above three laws they will end up using many of the BKMs. But at least then they will be using them because they were right for them, and not because they were right for the person who gave them their "Intro to SCRUM" course.

===> Late addition: of course the most important rule, rule '0' is: Like the samurai of old, the team lives to please the product owner.