Retained Powers Decree

The Retained Powers Decree, also known as Article 89 of the Occrean Terms of Surrender 4062, was a list of legal powers the governing body of the city of Occrea kept when its former nation, Kolobaden, was taken over by Crel Onar.
The document itself, at the time, was made more of a symbolic "we're not dictators" public relations stunt rather than something that was expected to be legally and politically significant. Nobody could have guessed that it would in later centuries not only become infamous but actually, ironically, lead to the city of Occrea becoming an independent state.
The relevant clause in question granted the city council permission to make the final decision concerning immigration status for any foreigner wanting to reside in Occrea. It did not, however, specify that this only applied if the foreigner in question was from the same planet. When Occrea opened up diplomatic relations with other planets, the central Crel Onar government tried to challenge Occrea's decision to allow refugees from other planets into their city and therefore into Crel Onar. However the Retained Rights Decree proved absolutely watertight and nothing the central government could do could overturn it.
By then, the formerly minor city of Occrea had grown to be the biggest and one of the most powerful cities on the whole planet. Diplomatic relations with other worlds only increased its influence. Occrea's values had become increasingly out of step with Crel Onar's politics and the tension was only increasing. As the row over interplanetary immigrants continued, and the Not On My Doorstep campaign grew in size and audacity, the pressure to find a resolution which would not lose Crel Onar the economic benefits that Occrea gave them also increased.
With no way to legally or politically force Occrea to toe the line, Occrean citizens divided over the issue and the Occrean government wanting autonomy, negotiations eventually began for an independence deal which suited both sides. The Independence Decree was agreed in 7845.