public international law - country of the question: Malaysia

this question is under the self-determination concept.

Some traders from Alpha discovered an uninhabited island in the Pacific Ocean in 1400. The island was 200 nautical miles from Alpha. From 1500, Alphan fishermen began to fish in the coastal waters of the island and started a small fishing village there. The island was called the Island of Beta. In 1550, the Government of Alpha sent a naval vessel to the Island of Beta, flew its flag on it, and pronounced its sovereignty over the island. Alpha re-drew its map in which the island was included in its territory. That year, the Alphan Government officers started to collect taxes from the people there.

In 1600, the Empire of Delta aggressed against Alpha's mainland and captured all its islands in the region. The Alphans in the Island of Beta fled to the mainland and other places.

In 1700, a religious group, the Spiritualists, who had fled from persecution in their native land, Gamma, settled in the Island of Beta. The Spiritualists paid annual tribute to Delta who let them reside there.

After 20 years of collecting tribute from residents of the Island of Beta, Delta no longer sent officers there. Under the leadership of their religious chief, the Spiritualists mapped the island, designed a flag for it, and built a lighthouse at the far end of it. Religious law of the Spiritualists started to be applied there. Their population increased. They built a city with a sea port, and commenced trading with neighouring countries. From 1800 onwards, the Island of Beta has been visited by several foreign leaders and has received foreign diplomats from several countries.

In 1980, when oil was discovered near the Island of Beta, Delta enacted legislation formally incorporating the island into its territory. This action was met with protests from Alpha and the Betans.

Analyse the legal position of the above dispute over the Island of Beta.