Many slogans are vacuous and aimed more toward the release of endorphins than conveying information. “No Justice, No Peace”is more robust than this, but it admits of interpretations that run from the noble to the demonic.
1.) The Natural Consequence Interpretation. The claim is a brief commentary on the definition of justice as the pre-condition of peace. Taken this way it’s a truncation of Martin Luther King’s claim (said previously) that peace is not merely the absence of tension but the presence of justice.
2.) The Explanation Interpretation. Systematic injustices are seen as being the cause of civil unrest, the subtext being that the injustices are severe, deliberate, and egregious while the civil unrest is understandable and sympathetic.
3.) The Right-to-Riot Interpretation. We acquire the right to riot in response to unjust treatment or an unjust jury verdict.
4.) The Thrasymachus Interpretation. Justice is simply the will of the stronger. If you don’t give us what we want in your “law enforcement” and “trials” then we’ll simply take it with riots and burning, and use the threat of this to extort your future jurymen into giving us what we want.