Kewajiban divestasi saham penanaman modal asing di dalam Undang-Undang Nomor 4 tahun 2009 tentang pertambangan mineral dan batubara beserta peraturan pelaksanaannya : studi kasus renegosiasi ketentuan divestasi dalam kontrak karya PT. Freeport Indonesia = Shares divestment obligation of foreign investment within Law Number 4 year 2009 regarding mineral and coal mining and its implementing regulations : case study renegotiation of divestment provision on contract of work of PT. Freeport Indonesia