The brothers of Trinidad & Tobago sought advice from the noble Shaykh 'Ubayd ibn 'Abdillaah al-Jaabiree (May Allaah preserve him) concerning the disagreement that occurs every year in the west, where a group of muslims start and stop their fast based on the sighting of the moon internationally, whereas another group goes with the local/regional sighting. Both groups have their evidences and scholars from Ahl Sunnah who support their respective positions.
[Q]: Requesting advice for those brothers who have disagreed on the matter of the obligation of fasting according to the land they live in or is it only when sighting for all of the Muslims all over the earth?
[A]: This is a matter that had been discussed in the old and previous times but what I have come to wallahu ‘alam, that those from the sons and daughters of the Muslims in Europe and USA are divided into two groups. The first group is those who have left the Muslim countries, they must fast according to the sightings of Muslim land that they left behind . The second group is those who are natives and citizens of the land they live in, they must fast according to the sightings of the most trustworthy country amongst them, and if there is a centre from the centres of the Muslims (in their country) that is trustworthy and this centre declared that the moon has been seen with the naked eye, then there is nothing on them except to follow that centre.
[taken from a tele-link session with Shaykh 'Ubayd al-Jaabiree (hafidhahullaah) and the brothers at Mpubs, Tobago and al-Ibaanah.info, Germany on August 12th 2012]