Mcgill won't accept you with an incomplete degree - you need to be finishing your undergrad prior to the anticipated start date, unless you are accepted through the CEGEP category (which won't happen if you didn't go to CEGEP).
@meandtheboysI meant to emphasize how difficult it may be not that it shouldn’t be done. I found it challenging because I had to complete degree requirements and requirements for a major in Finance in three years. It may be much more manageable if OP is in a less structured program.
@KidAyy OP still may be able to obtain on undergraduate degree so long as they complete at least one year of Law school. Many schools allow students to transfer JD credits to complete an undergraduate degree.