Anyone can form a group and call it a "militia".
In the event of a crisis (ie Katrina), this "militia" can act to aid the community and protect against lawlessness, within what the law allows any individual to do in that regard. For instance, in many states you can come to the defense of a person being attacked by criminals... it doesn't specifically state that you can't do so as part of an organized group, in most jurisdictions. Example: the Guardian Angels.
However, in order to legally act in an actual militia capacity (ie as a military force), would require state sanction and putting control of the militia under the Governor...which apparently they are seeking to do.
Don't see what would make it either a problem, or a big deal. It is in accord with the Constitution and with historical useage of "militia".