Does the Americans With Disabilities Act require accommodations for students whose disability prevents them from behaving ethically?
Behaving unethically, at least as far as it requires or deserves sanctions, requires an element of choice. If the person had no choice, e.g. because of a disability, then sanctions are not called for.
It is probably my lack of imagination, but I cannot think of an disability that requires students to act unethically.
As to how the law views this: talk to a lawyer or the legal department, or equal opportunities department of your university.