Is there a new law that states casino dealers who have been 1099 employees working about 8 hours a month now have to be W2 employees?

No, there is no specific law requiring this, but the fact is, dealers are almost always properly considered employees paid by/on a W2, not independent contractors (the correct term; not "1099 employees") under the labor laws. Whether someone is an employee or not has no relationship to how often or many hours they work; rather, it is based on the nature of the relationship between them and their employer and the employer's degree of control over them. 
An independent contractor (1099) is, as the term implies, largely independent: they are hired to do or create something, but can control what hours or when they do it (as long as they hit the overall deadline), where they do it to a large degree, and how they do it. Conversely, if the employer can tell the worker when and where to do the job, and also manage/direct the worker in how to do it, they are an employee, not an independent contractor. Temporary and part-time workers who work at a location determined by the employer, during hours the employer determined, and the employer can direct themin how they do their job, are almost always employees. An example of an independent contractor would be a freelance graphic artist who designs a logo or marketing piece for you working at his own studio/office on his own schedule, or a freelance bookkeeper who comes in 1 or 2 days a week to collect your business's records, but can analyze and spreeadsheet, etc. them at his/her office and email you the workproduct.