Laelius served under Pompeius Magnus as envoy and naval prefect in 49 and 48 BC, during the civil war against Julius Caesar.
[5]Laelius presented the Greek and Jewish witnesses at the trial, while his co-counsel, the son of Gaius Appuleius Decianus, handled Roman citizens who had been living abroad.
Flaccus may have won the case because of bias, but a general awareness of his guilt is indicated by his failure to advance to the consulship, an achievement that would have been expected based on his family history.
In February 49 BC, he was a special envoy to the consuls Claudius Marcellus and Lentulus Crus at Capua, with the task of urging their retreat to Brundisium.
Cicero's use of the word "respectable" (honestus) instead of "noble" (nobilis) to describe his family background suggests that he was not descended from the consular Laelii.