In most instances they are. What they do is marry one, then divorce them while remaining "spiritually" married to them. They marry the next for the easy name change stuff, then divorce and marry.... So forth.Ok while I agree that forced marriages are repugnant and that polygamy is nucking futs, if 3 or more consenting adults wish to be in a marriage what right does the state have to tell them no? Our government can tell them that they can only claim one spouse for tax purposes, that the heavy hammer of the state will come down on them if they don't support all their kids and they have to be on public assistance, but three or more consenting adults should be allowed to be in whatever relationship they want.
In this way they are never legally married to more than one. So long as they continue to do this and nobody complains and they are all of legal age the government cannot do anything to them.