This excerpt taken from the AKS 10-Q filed Nov 6, 2007.
ARTICLE VELIGIBILITY AND PARTICIPATION
5.1 Eligibility. Participation in this Plan shall be limited to Eligible Employees. An Eligible Employee may receive allocations of Company Matching Contributions in accordance with Section 5.1, and thereby become a Participant under the Plan. An Eligible Employee who becomes a Participant shall continue to be a Participant until such time as his Supplemental Thrift Account has been completely distributed to him or his Beneficiary.
5.2 Removal. The Administrator may remove any Participant from future participation in this Plan. Such removal shall not affect the removed Participants benefits under this Plan that accrued prior to the effective date of the removal.