We allow private usage of our pool by residents, (co-owners and tenants), per our condo by-laws, (approved at the AGM). Included in that text are the conditions, (numbers of people, times available cost etc). Anyone wishing to avail themselves of the facility have to seek permission of the management office and make a booking. In our case, the building manager would consult the committee, (including me), and I can tell you that approval would not be given for this, as it infringes the rights of all residents.
You should speak to the Juristic Person Manager and your management company, and ask who has approved it. I imagine your neighbours are also rather hacked off that they are excluded too, unless they are included because it is restricted to co-owners.