(c) Any person serving a mandatory minimum sentence for violating any provision of this section shall be eligible for parole after serving one-half of the maximum term of the sentence if the sentence is to the house of correction, except that such person shall not be eligible for parole upon a finding of any 1 of the following aggravating circumstances:(i) the defendant used violence or threats of violence or possessed a firearm, rifle, shotgun, machine gun or a weapon described in paragraph (b) of section 10 of chapter 269, or induced another participant to do so, during the commission of the offense;(ii) the defendant engaged in a course of conduct whereby he directed the activities of another who committed any felony in violation of chapter 94C; or(iii) the offense was committed during the commission or attempted commission of a violation of section 32F or section 32K of chapter 94C. A condition of such parole may be enhanced supervision; provided, however, that such enhanced supervision may, at the discretion of the parole board, include, but shall not be limited to, the wearing of a global positioning satellite tracking device or any comparable device, which shall be administered by the board at all times for the length of the parole.