"...which is what happens when you call the feds..."
―Malcolm Reynolds[src]

Also known as "the feds", federal agents were a law enforcement arm of the Union of Allied Planets. Agent McGinnis, was the leader of a "small battery" of Feds at Saint Lucy's hospital who managed to briefly apprehend River and Simon Tam and Jayne, but lost them again.

Most of the weapons that they use are the non-lethal sonic rifle and other weapons and gear, making them very different from the Hands of Blue.

They were similar to the Federal marshals.