The real answer is that the Coast Guard falls under the department of Homeland Security rather than the department of defense. Because of this, the coast guard can take actions overseas that the navy cannot without them being considered an act of war.
Harris828 t1_iwgmedd wrote
Reply to comment by Jim_from_GA in Navy, Coast Guard stop ship with 180 tons of Iranian explosive materials by millennium-wisdom
The real answer is that the Coast Guard falls under the department of Homeland Security rather than the department of defense. Because of this, the coast guard can take actions overseas that the navy cannot without them being considered an act of war.