In 1920, duelling was made legal subject to some strict conditions:
MONTEVIDEO, Uruguay, Aug 5 — The Chamber of Deputies has approved a bill suppressing existing penalties on duelling, provided certain conditions are fulfilled.
The penalties are suppressed under the bill, provided the seconds submit previously to a court of honor consisting of three members, the question of whether an offense justifying the duel exists and if so who is the offended party.
Blood banks weren't established until the 1930s, so being a blood donor could not have been a requirement.
While a court of honor met as recently as 1990, this law was overturned in 1992.
Uruguay's congress has rescinded a 72-year-old law that allowed disputes to be settled by a duel.
In 1990, police inspector Saul Claveria challenged La Republica newspaper publisher Federico Fasano to a duel over an article that linked Claveria to smuggling.
Claveria eventually withdrew his challenge, saying Fasano was not a worthy opponent.
The lower house approved rescinding the law earlier and the Senate followed suit on Wednesday. It now goes to President Luis Lacalle for signing.
I could find no sign of the law being re-enacted since 1992.