Hi,
Welcome to ehealthforum,
The vasectomy done can be reversed. If you are planning for pregnancy, he should consider visiting his doctor/Andrologist/Urologist for further evaluation and go ahead with the reversal operation to open up the Vas (semen analysis done after 1 month of the procedure showing good quality sperms will confirm the success of the procedure). For further clarifications and discussion, visit your doctor/gynecologist, or consider taking opinion from Infertility specialist.
Take care.