The Netherlands generally, although not always, extends its membership of IP treaties to Aruba. A concise list is provided on the website of the Bureau of Intellectual Property.
It is the Bureau of Intellectual Property that administers IP in Aruba. They have an informative website, although it is not clear if it has been updated since 2007 - it states it is celebrating its 20th anniversary having been instituted in November 1987.
Nevertheless, the website contains most information anyone should need to know in Aruba and if you are looking for a local patent or trademark agent then lists are provided. Aruba enjoys a reasonably high standard of living and perhaps we should therefore expect there to be funds available for a decent website.
Aruba is a quick registration jurisdiction when it comes to trade marks. Strangely, the forms are provided in .XLS format. They must be filed in Dutch or, the somewhat quirky but attractive looking, Papiamento.
The Netherlands has not extended the Madrid Protocol to Aruba (unlike with the other parts of the Kingdom of the Netherlands in the Caribbean). There is little appetite from local practitioners and with a population of little more than 100,000 it is doubted there are brand owners there with significant interests abroad to press for membership. Aruba has a historically strong independence movement and in line with the Dutch consociational style of Government, Madrid Protocol extension will not be imposed upon them against their wishes. Therefore, I anticipate Aruba will remain outside the Madrid family for the immediate future.