Bachelor's degree and NIC, EIPA 4+
The Delaware State Courts has their own policy called “ Delaware Certified Court Interpreters Program” include sign language interpreters. You may browse their website at:
Some hospitals have their own policy on sign language interpreters. They developed their own contract with interpreters who are willing to work with them.
None Required
"Unfortunately, at this time, there are no licensing requirements or monitoring procedures in place for freelance interpreters in Delaware, with 2 exceptions.

The first is the requirement that any interpreter, for any language, working in the courts, must have AOC approval or AOC certification. I believe that is standard in all states.

The second is a requirement that all "Interpreter / Tutors for the Deaf and Hard of Hearing" employed in public schools must receive a permit. This permit is granted based on RID Generalist Certification or an EIPA score of 4.0 on either the Elementary or Secondary Exams. Interpreters already working in schools, who do not meet the requirements, have until 2016 to comply." ~ Betsy Tucker, CI and CT
Governing Body
Delaware Office for the Deaf and Hard of Hearing (DODHH)
The permit to interpret in educational settings is renewed every five years but I'm not sure if there is any fee involved.
Bachelor's Degree in any field from an accredited college and holds national certification by RID or is a certified member of RID as an EIPA credentialed interpreter with 4+. An applicant shall disclose his or her criminal conviction history upon application for the Permit. Failure to disclose a criminal conviction history is grounds for denial or revocation of a Permit.
A Permit issued under the provisions of this regulation may be revoked upon a finding of conduct that meets the definition of “Unfit” in 2.0 of this regulation and must be revoked upon finding that the permit holder made a materially false or misleading statement in his or her permit application or upon finding that the permit holder failed to maintain the requirements for a Permit as designated in 3.0 herein.