Are Super Bowl Parties Illegal?
The law (U.S. Code, Title 17, Chapter 1, Section 110) says it's OK to operate "a single receiving apparatus of the kind commonly used in private homes" as long as you don't make a "direct charge" for it. It also distinguishes between private homes and public establishments.
That still leaves enough ambiguity to cause mischief. In one notorious case, NFL threats forced a church to cancel its Super Bowl Bash, as we reported a couple of years ago.
If you'd like to take in the details, Ars Technica explains all.