What does it mean to let a team self-organize? I am guessing that it varies some from team to team, but I tend to think of concepts like managers trusting the team's opinion on what they need to get things done, empowering them and giving them the freedom to determine their best composition, structure, and timelines.
I have read a lot lately about why that makes sense; how letting the people closest to the work make decisions about it makes sense, and how empowering the teams allows for the best decisions to be made.
So .... why would people say this? Well, again, I am sure you can read all about it from the Ron Jeffries, or Ken Schwaber, or Mary Poppendieck people of the world. Following my precedent, let me be the one to give you a whole bunch of reasons why preventing self-organization *doesn't* work (speaking from experience, of course).
What about team composition? Recently, one member of our team was taken off the team by upper management. That team member had previously been "voted back onto the island" by the team. It bothered me that after our team had chosen for that team member to be included as part of the team, that a member of management would just decide to take them off. What concerned me more was the motivation for doing it (as reported by mgmt): the team has complained that we don't focus enough on the project that has been pounded into our heads as our number 1 priority. This team member focuses mainly on other things, so by removing him from the team, the rest of the team should feel more focused.
The team's response was predictable. They felt like their decision had been undermined by mgmt. The team does not feel empowered to make decisions about what is best for them, and worse, recognizes that the root problem has not been addressed. Removing people from the team does not magically fix the fact that the team is not allowed to focus on the number 1 goal.
A team that is not empowered to make decisions feels disrespected. They feel like they are not trusted and cannot do their best job. These teams do not give their best effort. They stop taking the time to think through everything as thoroughly as they do when they feel passionate, trusted, and empowered. Nobody wins in this situation.