Well, PMI can impose any rule it wants to protect its reputation and the reputation of its credentials.
I personally think the ban for life is a bit harsh (if possible, can you tell the others here how you were banned? Were you cheating on the PMP exam?). I think there should be a better way to handle those that do not adhere to PMI's rules.
I advise you to contact PMI directly or better yet, through your local PMI chapter. I think the local chapter might have some influence within PMI which may help your cause.
In any case, you can go with PRINCE2 or you can do an MBA in project management at a decent university (which, in my opinion, is better and more prestigious than the PMP).