Former President Jimmy Carter refuses to cancel his keynote address for the ISNA, a terrorist front linked in the past to providing millions of dollars to Hamas who is designated by the U.S. as a terrorist organization. ISNA was officially designated an un-indicted co-conspirator by the Justice Department.
By giving the keynote address and aiding in the fundraising of ISNA, he may be in violation of Section 18 of the U.S. Code § 2339B by Providing support or assistance to a designated foreign terrorist organization
Former Presidents are not exempt from the law.