(a) General rule.--The capital of a credit union shall consist of the payments that have been made to it on shares.

(b) Automatic lien.--The credit union shall have an automatic lien on the shares or share certificates of a member for any sum due it from such member or for any loan endorsed by him.

(c) Share transfer restriction.--Shares of a credit union shall be transferable only to other members of the credit union.

(d) Share insurance required.--The shares representing the savings of members shall be insured in such amounts as provided by the National Credit Union Administration or other share insurance fund approved by the department to insure the shares of credit unions. A credit union that has not obtained share account insurance from the National Credit Union Administration or other share insurance fund approved by the department may not, without the prior written approval of the department, accept payments from its members for the purchase of shares.