Hello John,
Frustratingly, none of Apple's MacBook Pro (or MacBook) ranges, current or otherwise, can accept more than 16 GB (by any means).
At this point in time, if you want a laptop with more than 16 GB then it has to be a Windows/PC one. (E.g. some companies such as Dell make laptops that can accept up to 64 GB.)
Apple's current 27" iMac model can accept 64 GB, however, as can their Mac Pro (although the later is very expensive and hasn't been updated for a few years).