when working with a radio group, the list of elements will have a main option for radio group:
WAATKRegistrationForm.memb_typ_us
and an indexed option for each element in the radio group:
WAATKRegistrationForm.memb_typ_us[0]
WAATKRegistrationForm.memb_typ_us[1]
the index at the end refers to specific radio buttons in the group. you should apply the validation to the main radio group:
WAATKRegistrationForm.memb_typ_us
In the code you provided, i do not see any validation applied to the radio group, only the "first_usr", "last_usr" and "email_usr" elements have validation applied.