If the alcohol was in plain view, no warrant needed. Basically trunk, glove box that is locked is the only thing you can fight. You had an expired tag, your gonna pay the fine regardless, they may reduce it if you show it's registered but with a possession of alcohol ticket you may not get that lucky. If I was the judge no reduction in fine for either. Next time keep the alcohol in the trunk and don't drive with expired tags and all your problems would be solved.