The principles of a free constitution are irrevocably lost, when the legislative power is nominated by the executive.

Gibbon’s sentence articulates a core constitutional principle: representative government depends on the legislature’s independence from the executive. If the executive can nominate (i.e., appoint or effectively choose) the legislative power, the separation of powers collapses and the legislature becomes an instrument of the ruler rather than a check upon him. The warning is aimed at the mechanisms by which free constitutions are hollowed out without necessarily abolishing their forms—elections, assemblies, and laws may remain, but genuine accountability is lost when lawmaking authority is controlled from the executive. The emphasis on “irrevocably” underscores how difficult it is to restore liberty once institutional dependence is established.