I don’t think it would fly in a discrimination suit or harassment suit. They are treating you like any other employee. They’re not harassing you because you have ADD. They’re treating you exactly as they would treat any other employee who isn’t getting the job done. When you took work home, you were deliberately violating company policy, and they responded in the same way they would respond to any other employee who did the same. And they’re understandably frustrated with the fact that (from their point of you) you seem to be making excuses. The first thing an employee should do would be to advise the employer (in writing) that the employee has been diagnosed with a disability that may require accommodation in accordance with ADA, and request a formal meeting in order to discuss what accommodations might be reasonable. That way, everyone’s on the same page.
The employer is required to make reasonable accommodation for a disability, but this needs to be established in a formal meeting, where employer and employee sit down together and discuss what accommodations are necessary for the employee to do the job. An employer is not required to make accommodations that cost the company undue time or money. is only required to make reasonable accommodation (such as allowing an office change if the current office is too noisy to focus). Taking work home might seem to be a reasonable accommodation, but it’s more serious than most employees realize. It amounts to unpaid time, and the company can get in serious legal trouble over it, if the employees involved receive an hourly wage. The employer is not required to simply give an employee a pass on missed deadlines and unfinished projects, because these kinds of things affect other employees and cost the company time and money.