Section 9I. A governmental unit which has accepted the provisions of section ten and which accepts the provisions of this section as hereinafter provided, shall consider an employee on a military leave of absence because said employee is a member of the army national guard or air national guard or a reservist in the armed forces of the United States called to active service in the armed forces of the United States, for the purposes of this chapter, to be deemed to have been granted leave without pay, and subject to the rules and regulations of the appropriate public authority, said employee shall make payment of the portion of the total monthly premium or rate that would have otherwise been deducted from his salary, wages or other compensation.

For purposes of this section, the term ''active service'' shall not include active duty for training in the army national guard or air national guard or as a reservist in the armed forces of the United States.

This section shall take effect in a county, except Worcester county, city, town or district upon its acceptance in the following manner:— in a county by vote of the county commissioners; in a city having a Plan D or Plan E charter by majority vote of its city council; in any other city by vote of its city council, approved by the mayor; in a district, except as hereinafter provided, by vote of the registered voters of the district at a district meeting; in a regional school district by vote of the regional district school committee; in a veterans' services district by vote of the district board; in a health district established under section twenty-seven A of chapter one hundred and eleven by vote of the joint committee; and in a town by vote of the town meeting or town council.