Do I have a legal obligation to make multimodal assignments accessible, using principles of universal design?
Yes and No.
Under Section 504 of the Rehabilitation Act and Titles II and III of the Americans with Disabilities Act, institutions of higher education (both public and private) have a legal obligation to provide reasonable accommodations to make the classroom and learning materials accessible. Often this responsibility falls under the provisions of a disability resource office. However, instructors do have a legal obligation to ensure that students can use their accommodations in the classroom (e.g. an instructors cannot ban a students’ use of a laptop if they have an accommodation that allows it). So, while instructors have no legal obligation to use principles of Universal Design or to proactively make their assignments accessible to disabled students, it is a good pedagogical practice do so.
For more information about legal considerations, follow this link to Legal Considerations.