1890, Robert Franklin Pennell, History of Rome:His valor, wisdom, and justice made him justly popular, but caused him to be regarded with suspicion at Rome.
With a just or fair use of language; with good reason, properly.
2012, Jay Newton-Small, ‘Gangless in Glasgow’, Time, 1 Oct 2011:But the city on the River Clyde can justly claim to have turned the tide.
1603, John Florio, translating Michel de Montaigne, Essays, II.14:It is a pleasant imagination to conceive a spirit iustly ballanced betweene two equall desires.