For what reasons might the twenty-fifth amendment be used to replace a president?

The 25th Amendment outlines the rules of succession to the U.S. Presidency and Vice Presidency in the event of either or both of them dying, withdrawing or being removed from office.

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.