If their 10-year GC card is still not expired, they can enter US, they will then be admitted and stay from 30 days (if not fight for GC) to forever (if successfully reinstate GC).
If GC plastic card is expired and they don't have immigrant intent anymore, fill I-407 to give up GC at US consulate so they can be issued B visa after that.
Or if they do want to live in US forever, apply SB1 at BJ or GZ consulate.
If GC plastic card is expired and they don't have immigrant intent anymore, fill I-407 to give up GC at US consulate so they can be issued B visa after that.
Or if they do want to live in US forever, apply SB1 at BJ or GZ consulate.