There is no such rule. Any employee, temporary and "permanent" full-time, in NY State is considered at-will and can be terminated at any time for any reason. Unless you have a written contract entitling to you for term employment, it doesn't matter who cuts your check, the temp agency or the employer's payroller.
If an employer assumes day-to-day control over the temp, the temp may legally be considered an employee (but still at-will and subject to random termation). As long as the temp agency complies with wage & hour, benefits, and general employment law typically there is no net impact. If however (while you quesiton doesn't get at it) if the temp agency is denying you benefits and OT to which you would be entitled as a FT regular employee, there are potential problems and claims and you should seek counsel.