There are numerous criteria that law schools may consider when making admissions decisions. Law schools vary in the relative level of importance they place on these two criteria, though most seem to weight LSAT score more heavily.
Most law schools compute an Academic index for each applicant.
This index is some combination of the applicant's GPA plus LSAT score. Applicants in this pile are virtually assured of being admitted to the school. Applicants in this pile are immediately rejected from the school. Unfortunately, the committee will not even look at the rest of the file. Applicants in this pile can be either accepted to or rejected from the school, based on their indices plus everything else in the file.