Well...no. The law is whatever the local administration says it is. Recommendation T/R 61-01 does specify that the local prefix comes first, and I agree with Jan that this is the best arrangement. However, if you have a license that says, for example, that your callsign is K4AJA/VP9 then that's what you must sign.
The FCC doesn't care whether its licensees append portable designators indicating their DXCC location, and also doesn't care whether it goes in the front or the back if either the contest rules or personal preference dictates one or the other. FCC Rules, 97.119(c):
(c) One or more indicators may be included with the call sign. Each indicator must be separated from the call sign by the slant mark (/) or by any suitable word that denotes the slant mark. If an indicator is self-assigned, it must be included before, after, or both before and after, the call sign. No self-assigned indicator may conflict with any other indicator specified by the FCC Rules or with any prefix assigned to another country.
On Friday, November 2, 2018, 12:15:58 PM EDT, Rich Seifert <ke1b@...> wrote:
I (and many others here in EU) always use the prefix of the country where I am before my own call. So 9A/PA4JJ or PJ2/PA4JJ
In my opninion this is how it should be done because you are operating from a different country prefix than your own.
It’s not only your (correct) opinion, it’s the LAW. Stations operating outside their home DXCC entity MUST use the national prefix of the country they are in, followed by their home callsign (when this is their call).
From Jamaica, you should have signed 6Y/K4AJA.
(FYI: The only exceptions are USA stations operating in Hawaii or Alaska (which are separate DXCC entities); they sign K1ABC/KL7 or K1ABC/KH6. Also, USA stations operating in Canada sign K1ABC/VE3 or similar. It’s because we have a separate radio treaty with Canada.)
Rich KE1B (and often VP5/KE1B, 9Y/KE1B, EA8/KE1B, and many more)