205 ILCS 205/2001.35

(a) "Control" shall mean either ownership of stock, or the power to vote and dispose of stock in a manner that directly or indirectly causes changes in savings bank management, ownership, structure, or policies. Any change in ownership of stock, or of rights related to stock, that would result in direct or indirect ownership of 20%, or of a lesser amount that would entitle the holder to elect one director shall be presumed to be a change of control. Any change in ownership must be approved by the Commissioner.

(b) Notwithstanding the provisions of this Section, the Commissioner may define "control" by rule and regulation, in a manner to ensure uniformity with federal law, regulation, and usage.