14 U.S. Code § 99 - Enforcement authority

Subject to guidelines approved by the Secretary, members of the Coast Guard, in the performance of official duties, may—
carry a firearm; and
(2) while at a facility (as defined in section 70101 of title 46)—
make an arrest without warrant for any offense against the United States committed in their presence; and
seize property as otherwise provided by law.
(Added Pub. L. 111–281, title II, § 208(a), Oct. 15, 2010, 124 Stat. 2912.)