No one was admitted to the lists, who could not prove himself, at least maternally, to be one of four descents and display a legitimate coat armour.

-From Inquiries into the Origin and Process of the Science of Heraldry in England by James Dalloway, p90

Essentially, in order to compete in a tournament, you had to have at least one great-great-grandfather, if not more, who was noble and bore arms.

…[I]t is recorded that Philippa, queen of king Edward the third, very narrowly escaped with her life, upon the falling down of a scaffold at a tournament held in Cheapside.

-From Inquiries into the Origin and Processes of the Science of Heraldry in England by James Dalloway, p89

Arms of Louis I of Hungary and Poland

 

King of Hungary, 1342-1382, and Poland, 1370-1382 (1326-1382)

Blazon: Per quarterly, I per pale barry of eight gules and argent (Hungary ancien) and azure seme des lis or (France ancien); II gules an eagle displayed argent, armed and crowned or (Poland); III gules a cross patriarchal pate issuant from a crown upon three mounts in base all proper (Hungary moderne); IV azure three lion’s heads couped, caboshed, and crowned or, langued gules (Dalmatia)