Barbarians must be non-lawful (at least if they want to keep their Rage), while Knights must be lawful.
Then was there one that Sir Launcelot had sent unto
that place for to espy what time the queen should go unto
her death; and anon as he saw the queen despoiled into
her smock, and so shriven, then he gave Sir Launcelot
warning. Then was there but spurring and plucking up
of horses, and right so they came to the fire. And who
that stood against them, there were they slain; there might
none withstand Sir Launcelot, so all that bare arms and
withstood them, there were they slain, full many a noble
knight. For there was slain Sir Belliance le Orgulous,
Sir Segwarides, Sir Griflet, Sir Brandiles, Sir Aglovale,
Sir Tor; Sir Gauter, Sir Gillimer, Sir Reynolds' three
brethren; Sir Damas, Sir Priamus, Sir Kay the Stranger,
Sir Driant, Sir Lambegus, Sir Herminde; Sir Pertilope,
Sir Perimones, two brethren that were called the Green
Knight and the Red Knight. And so in this rushing and
hurling, as Sir Launcelot thrang here and there, it
mishapped him to slay Gaheris and Sir Gareth, the noble
knight, for they were unarmed and unware. For as the
French book saith, Sir Launcelot smote Sir Gareth and
Sir Gaheris upon the brain-pans, wherethrough they were
slain in the field; howbeit in very truth Sir Launcelot
saw them not, and so were they found dead among the
thickest of the press.
Alas that ever this war began. Now fair fellows, said the king,
I charge you that no man tell Sir Gawaine of the death
of his two brethren; for I am sure, said the king, when
Sir Gawaine heareth tell that Sir Gareth is dead he will go
nigh out of his mind. Mercy Jesu, said the king, why
slew he Sir Gareth and Sir Gaheris, for I dare say as for
Sir Gareth he loved Sir Launcelot above all men earthly.
That is truth, said some knights, but they were slain in
the hurtling as Sir Launcelot thrang in the thick of the
press; and as they were unarmed he smote them and wist [knew]
not whom that he smote, and so unhappily they were
slain
Wasn't there something about the 1E Cavalier having the ability to have any alignment possible?
Barbarians can only be human and cannot duel class.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.