Sports law is not a single body of doctrine but three legal systems layered on top of one another — contract, antitrust, and labor — and almost every dispute in the industry is really a fight about which one controls. This UpLaw guide maps the whole field: how leagues govern themselves and where a commissioner's "best interests" power runs out; why American Needle refused to treat a league as a single entity and what that means under Sherman Act § 1; how the nonstatutory labor exemption of Brown v. Pro Football immunizes salary caps, drafts, and free-agency rules that would otherwise be per se illegal; how the standard player contract, the salary cap, and grievance arbitration actually work, including why courts almost never disturb a commissioner's award after the Brady litigation; how agents are regulated by unions, by SPARTA, and by the Uniform Athlete Agents Act; and how the NCAA's amateurism edifice collapsed from O'Bannon through Alston into the NIL era, the House settlement, and the still-open question whether college athletes are employees. It closes with Title IX, athlete publicity rights, sports betting after Murphy v. NCAA, doping and CAS arbitration, concussion and injury liability, and franchise relocation. Two invented running hypotheticals — a college quarterback signing an NIL deal and a professional linebacker grieving a suspension — carry the doctrine from the abstract to the negotiating table. Because NIL rules, college-athlete employment status, and betting regulation are all changing month to month, the guide teaches the framework and flags every place you must verify the current rule.