The prisoner in this verse is intelligent and thoughtful. The previous line suggest perhaps he could have been a successful lawyer in other circumstances. Instead he can “claim sovereignty” or authority because he’s protected by the Moors.

This refers to The Moors, or Moorish Law. Moorish-Americans follow a sect of Islam shaped by Noble Drew Ali, the movement’s founder. They frequently append “El” or “Bey” to their last names; African-American prisoners often convert to Islam while incarcerated.

As mentioned in the Wikipedia article, there’s some crossover between Moors and the sovereign citizen movement. Sovereign citizens usually believe that they’re only answerable to their own interpretations of common law (precedent set by court cases). They often reject the federal government’s legitimacy and refuse to pay taxes.
They may also use unorthodox legal tactics to try and win a case. For example, some sovereign citizens believe that writing their names like “x, of the family y” will grant them immunity from prosecution.
It’s unsurprising that Prisoner 1 runs into a few of ‘em in jail.

Stefani compares herself and Love to fired-up schoolkids, further elaborating on the song’s high school metaphor. In school, there’s often a popular mean girl (Love), but now the outcast is coming for her throne.