Why was that battle fought after the peace treaty was signed?

The Last Battle of the war of 1812. ... Many people think the battle of New Orleans ended the War of 1812, but this is not the case. A peace treaty, the treaty of Ghent had been signed before the battle started, but news of the treaty did not arrive in America until after the battle was fought

Assemblies do not have written codes of laws. laws are matters for magistrates and courts, not assemblies. codes of law are things such as civil law, criminal law, and constitutional law. what assemblies have are procedures regarding debating, voting and other business they might carry out.  also note that rome had three assemblies: the assembly of the soldiers, the assembly of the tribes, and the plebeian councils.