Green Party Candidate for Governor of California arrested - Hustings US style

An astonishing story here how the Green Party's candidate for Governor of California was not allowed to participate in the hustings and they were limited to the two big parties. Greens demonstrated outside and when she managed to get a ticket to enter she was grabbed by security guards and then arrested. Is this the way that elections should be conducted in "the home of the brave and the land  of the free?" Perhaps time for a UN investigation into election processes in the USA.