Re:How can they do this? (Score 1)

Usually how this works is Congress passes an incredibly vague law, like a law saying that the US Mint has the power to protect the value of our money, and then Congress adds that they leave it up to the administrative agency (the mint) to fill in the "details" of the law such as what protecting money means. The administrative agency then tells the world what this impossibly vague law really means, which has the practical effect of passing a new law.