Bretonnian Paladin Standard Bearer
 

When the option is chosen to carry the battle standard, it disallows the character from buying a shield - or, for that matter, a lance, or morning star.

sry, this is what the army list says for bretonnians :~(

Yes some army lists specifically state that if you upgrade to a BSB then you lose some equipment options.
IMO it should be this way for all armies but alas it is not.

i thuink they are changing it with each new army, but the old ones still work the old way afaik, unless it is faqd/erratad for them

To make up for this on the BSB take the Gromril Great Helm and the Sword of Might. Then the BSB has a 2+ AS and ST 5, but alas no Magic Banner. Or just use him straight up with a magic banner with a 3+ AS and ST 4 and maybe the Virtue of Discipline (Never outnumbered)