tribal character of a petitioner to the date of the last such previous acknowledgment. If a petitioner provides substantial evidence of unambiguous Federal acknowledgment, the petitioner shall only be required to demonstrate that it meets the requirements of section 7 to the extent required by this section. A determination of the adequacy of the evidence of previous Federal action acknowledging tribal status shall be made during the technical assistance review of the documented petition conducted pursuant to section 10(b). (b) Evidence Evidence to demonstrate previous Federal acknowledgment includes evidence that the group— (1) has had treaty relations with the United States