Erwin Chemerinsky is dean of the UC Irvine School of Law.

Not surprisingly, the Supreme Court on Monday agreed to decide the constitutionality of the individual mandate in the Affordable Care Act, the healthcare reform package passed in 2010. Under current constitutional law, this should be an easy case to predict — the law is clearly constitutional. But what complicates the decision and makes the result unpredictable is whether the justices will see the issue in terms of precedent or through the partisanship that has so dominated the public debate and most of the court decisions so far.

The primary issue before the Supreme Court is whether Congress' power to regulate commerce among the states gives it the authority to require that individuals either purchase health insurance or pay a penalty. The Supreme Court has repeatedly held that under the commerce clause, Congress may regulate economic activity that, taken cumulatively across the country, has a substantial effect on interstate commerce.

Thus, under current law, there are two questions: First, is Congress regulating economic activity? Second, if so, looked at in the aggregate, is there a substantial effect on interstate commerce?...