I’ve started reading The Unwritten Rules of Baseball by Paul Dickson, which is pretty neato so far.
In it, he mentions a legal case from 2006 about being hit by pitches. Some background from the opinion by Justice Kathryn M. Werdegar:
During an intercollegiate baseball game at a community college, one of the home team’s batters is hit by a pitch. In the next half-inning, the home team’s pitcher allegedly retaliates with an inside pitch and hits a visiting batter in the head. The visiting batter is injured, he sues, and the courts must umpire the dispute.
The court ruled that, even though the rules of baseball state that a pitcher can’t intentionally hit a batter, it’s commonly accepted as an “inherent risk of the sport” and so can’t be sued over in this way.
Being intentionally hit is likewise an inherent risk of the sport, so accepted by custom that a pitch intentionally thrown at a batter has its own terminology: “brushback,” “beanball,” “chin music.” In turn, those pitchers notorious for throwing at hitters are “headhunters.” Pitchers intentionally throw at batters to disrupt a batter’s timing or back him away from home plate, to retaliate after a teammate has been hit, or to punish a batter for having hit a home run. (See, e.g., Kahn, The Head Game (2000) pp. 205-239.) Some of the most respected baseball managers and pitchers have openly discussed the fundamental place throwing at batters has in their sport. …
It is true that intentionally throwing at a batter is forbidden by the rules of baseball. (See, e.g., Off. Rules of Major League Baseball, rule 8.02(d); National Collegiate Athletic Assn., 2006 NCAA Baseball Rules (Dec.2005) rule 5, § 16(d), p. 62.) But “even when a participant’s conduct violates a rule of the game and may subject the violator to internal sanctions prescribed by the sport itself, imposition of legal liability for such conduct might well alter fundamentally the nature of the sport by deterring participants from vigorously engaging in activity that falls close to, but on the permissible side of, a prescribed rule.” (Knight, supra, 3 Cal.4th at pp. 318-319, 11 Cal.Rptr.2d 2, 834 P.2d 696.)
So there is legal precedent in the United States that, if you get hit by a pitch, you have to suck it up.