If New York City bans big sugary sodas, what's next? Large slices of pizza? Tubs of movie-theater popcorn? The 16-ounce strip steak?

Opponents of the proposed ban may use that slippery-slope argument -- along with other legal strategies -- to try to block the rule.

Bennett Gershman, a professor at Pace University, argues that the ban would run afoul of the U.S. Constitution's Commerce Clause by imposing a burden on interstate business.

But Rick Hills, a New York University law professor, scoffs at that idea. He says that line of reasoning has never been used to strike down health and safety regulations regarding what can be sold in a state.

(Copyright 2012 by The Associated Press. All Rights Reserved.)