The “duties, rights, prerogatives and immunities” of American diplomats in Cuba is spelled out in a 1928 agreement that was signed in Havana and put into law in the U.S. in 1932. I learned that bit of diplomatic trivia from the State Department’s 130-page manual on Consular Notification and Access.
Excerpts from the 1928 agreement are below:
States may refuse to accept consuls appointed in their territory or subject the exercise of consular functions to certain special obligations.
In the absence of a special agreement between two nations, the consular agents who are nationals of the state appointing them, shall neither be arrested nor prosecuted except in the cases when they are accused of committing an act classed as a crime by local legislation.
In criminal cases, the prosecution or the defense may request attendance of consular agents at the trial, as witnesses. This request must be made with all possible consideration to consular dignity and to the duties of the consular office and shall be complied with by the consular official.
Consular agents shall be subject to the jurisdiction of the courts in civil cases, although with the limitation that when the consul is a national of his state and is not engaged in any private business with purposes of gain, his testimony shall be taken either verbally or in writing, at his residence or office, with all the consideration to which he is entitled.
Consuls are not subject to local jurisdiction for acts done in their official character and within the scope of their authority. In case a private individual deems himself injured by the consul’s action, he must submit his complaint to the government, which, if it considers the claim to be relevant, shall make it valid through diplomatic channels.
In respect to unofficial acts, consuls are subject, in civil as well as in criminal matters, to the jurisdiction of the state where they exercise their functions.
The official residence of the consuls and places used for the consulate’s offices and archives are inviolable and in no case may the local authorities enter them without the permission of the consular agents; neither shall they examine nor seize, under any pretext whatsoever, documents or other objects found in a consular office. No consular officer shall be required to present his official files before the courts or to make declaration with respect to their contents.
When consular agents are engaged in business within the territory of the state where they are exercising their duties, the files and documents of the consulate shall be kept in a place entirely separate from the one where private or business papers are kept.
Consuls are obliged to deliver, upon the simple request of the local authorities, persons accused or condemned for crimes who may have sought refuge in the consulate.
Consular agents, as well as the employees of the consulate who are nationals of the state appointing them, not engaged in business with purposes of gain, in the state where they perform their functions, shall be exempt from all national, state, provincial, or municipal taxes levied upon their person or property, except such taxes as may apply to the possession or ownership of real estate located in the state where discharging their duties or to the proceeds of the same. Consular agents and employees who are nationals of the state they represent, are exempt from tax on the salaries, honorariums, or wages which they receive in return for their consular services.