First let me say that I am NOT arguing for minarchism in the least, and that is not what I mean by "constitutional anarchy." Let me also say that the term "constitutional anarchy" is one I made up, and so you should probably read the following explanation before answering. Sorry if it's a lot to read, but reading is necessary to understand my point.
What I mean by "constitutional anarchy" is the idea that an anarchist community, in its formation, should draw up a list of (edit:) specific aspects of community and personal life (end edit) that should be respected by everyone in the community, regardless of the circumstance. Kind of like the Bill of Rights, but agreed upon by everyone, not just rich white guys. Noncompliance would be punished by ostracization or some other kind of negative social sanction (for more information, check out the various questions on this site about anarchists dealing with crime). Participation in the community, and thus agreement to follow the outline of the constitution, would be completely voluntary, and different communities wouldn't be in any way obligated to have the same constitutions. People could very easily "shop" for a community with a constitution that they preferred, or if they wanted to change the constitution, they could take it up with the community.
These constitutions would not in any way restrict personal freedoms, except as they relate to the well-being of other members of a community. It doesn't matter what you do, as long as you don't hurt other people. This is a well-established anarchist credo, and a constitution would simply clarify that statement in relation to the community.
I know that many people will make the argument that by its nature, an anarchist society will never have atrocity or inequality and there is no reason to create a list of "rights" because every right that a person could possibly have would already be respected, but I don't believe that's true. For example, the issue of sex atrocities and the people who commit them comes up often, and there has never been a really good answer given, answers are usually vague and noncommital. (The "just let the family deal with it as they see fit approach" does NOT work. Often it results in feuding clans, which results in the creation of authority and institutionalized violence). A community with a concern for the sexual well-being of its young children could draw up a constitution that states that children incapable of explicitly stating consent and giving a clearly reasoned explanation of their consent (which would eliminate most kids under 13) have the right not to be pressured to have sex, and a girl who is not old enough to safely have a child without a serious risk to her wellbeing has the right to not be pressured with sex (eliminates most girls under 16). If a person violates that, they would become subject to punishment by the community. If a person doesn't like that, and I'm sure some anarchists wouldn't like the idea of that kind of restriction, they could simply find another community without that kind of constitution, or without any constitution at all (though I imagine most families with young kids, especially girls, would choose to live in communities with more protective constitutions).
Also, as an irrelevant side note I want to mention the fact that this American obsession with ridiculously young girls is probably a side-effect of a pedophile culture that doesn't value or respect womanhood. Women in most traditional cultures don't generally have their first child until they are in their twenties.
If a community felt it appropriate, it could even be helpful to outline methods of "justice"(another loaded term, but basically I mean the way of dealing the appropriate consequences for individual actions, not the consequences themselves. Those would need to be decided individually, per case) in the constitution. For example, as I mentioned, family vengeance quickly leads to clan warfare, which creates a violent, authoritarian culture. Instead, I might propose a method of "trial by open, voluntary jury," in which the entire community is allowed to weigh in on the issue before a punishment is dealt, helping to make sure that just one group of people, like an angry family, isn't exercising sole authority over that person's fate.
Oh, and finally, this constitution is not concrete. There is no centralized state enforcing it, there is no authority inherently belonging to it, it is simply a list of suggestions that the members of the community request that each other follow on the potential penalty of social punishment. If a community happened to become divided on an issue about the constitution, it could easily divide itself into two halves, with people simply joining the half that they preferred. Communities are not concrete either.
I know that this idea of a "constitutional anarchy" will probably be rejected by purists, but it might have some promise. Let me know what you think. Even if it has some issues that I'm not seeing, it's a flexible system. Oh, and yes, I'm most sympathetic to the anarcho-communist school of thought, so you can probably see where I'm coming from in that context (and now all the post-leftists can make fun of anarcho-communism in retaliation).
edited to fix tags