Going by memory on this, but I think the USA rule is that you can use any glove you want at any position. I looked this up when I saw a pitcher using a first baseman's mitt and was surprised that it was legal. Not sure how a catcher's mitt would help at 1B, though.
Some of the new catchers mitt are like hybrids ,, my DD has a Worth Liberty catchers mitt and her TB coach had her playing 1b a few times and really did well so i bought her a Worth/Rawlings Liberty 1st basemens mitts for the times she does play 1st she prefers the catchers mitt saying it just feels better . On the other side her HS coach will not let her use her catchers mitt at 1st base so old school is he )