Yet in the "Trent Affair" the British Government protested the stopping of a British ship by a United States Man of War and the arrest of two Confederate States diplomats which were under the protection of the British Government.

http://www.state.gov/r/pa/ho/time/cw/17612.htm

http://www.civilwarhome.com/trent.htm

The United States was forced to realize those diplomats and sent them on to England on their mission because of British threats to drop their neutrality and enter the conflict on the side of the Confederacy.

That by itself showed that England considered Confederate States diplomats as being protected under international law. Which would not have been the case had that Conflict been a rebellion as styled by the United States Government.

The British viewed it as the same as when the 13 Colonies asserted their independence from the British empire. And the fact that the French came to the aid of the colonies against the British strained English/French diplomatic relations for years. Remember a couple of fellows named Napoleon and Wellington?