if you are pre-2006 i think you could do two majors under com/law but restricted to the accounting/finance or finance/IBUS combinations
post-2006: im not so sure, you would have to check how many senior credits points you would need to satisfy a major and the total credit points taken up by law...
you can change it though the law faculty apparently, u dont have to go through UAC. Thats what one of the associate professors said in one of those welcome sessions.