Section 23A. No person, during the continuance of a strike, lockout or other labor trouble among his employees or those of another person, shall directly or indirectly employ or procure for the protection of such employees any armed guards other than watchmen regularly employed by such person, police officers or persons licensed under sections twenty-three to thirty, inclusive, of chapter one hundred and forty-seven or employees of such licensees; provided, that the foregoing shall not authorize the employing or procuring as aforesaid of any such licensee unless he shall have been so licensed at least two months prior to the commencement of such labor trouble, or of any employee of such a licensee unless such employee is a citizen of Massachusetts, and shall not have been convicted of a felony. Any person violating this section shall be punished by a fine of not more than two thousand dollars or by imprisonment for not more than six months, or both.