The portion of the costs of a program, project, or activity provided by a grant under subsection (a) of this section may not exceed 75 percent, unless the Attorney General waives, wholly or in part, the requirement under this subsection of a non-Federal contribution to the costs of a program, project, or activity. In relation to a grant for a period exceeding 1 year for hiring or rehiring career law enforcement officers, the Federal share shall decrease from year to year for up to 5 years, looking toward the continuation of the increased hiring level using State or local sources of funding following the conclusion of Federal support, as provided in an approved plan pursuant to section
3796dd–1
(c)(8) of this title.