Punctuation when referring to "US Copyright law"

You'll get different answers depending on who is giving them. The most widely used guide, The Chicago Manual of Style, can't quite make up its mind:

    "U.S." or "US." Except in scientific style, U.S. traditionally appears with periods. Periods may nonetheless be omitted in most contexts. Writers and editors need to weigh tradition against consistency. In running text, the abbreviation (in either form) is permissible when used as an adjective, but United States as a noun should be spelled out.

I would go with U.S. Some may object to US, but the periods should be accepted everywhere.

It is punctuated "U.S." in Associated Press (AP) style, but I doubt you're writing a newspaper article.