This reminds me of a "journalist", who joined all the political parties once, just to be ligitimite attendant to some sessions or meetings otherwise closed to the press.
He is/was more like a provocateur than a real journalist, but he did write articles for the back page to a Danish tabloid newspaper. Eventually, the parties found out about it, but still I think they don't have rules against it, because normally noone does it. Either you support one party or the next, not two or all of them. But it's kind of funny though...