Green’s Dictionary of Slang

(orig. US) a lawyer, with the implication of being an astute one.

1939		I. Brecher At the Circus [film script] [...] with the legal eagle on your case, the money is practically in your pocket.
1947		Billboard 5 July 20: Legal eagles predict a procession of court cases in which larger unions [...] probably will take the lead.
1955		B. Schulberg On the Waterfront (1964) 208: We’d better have a meeting with [...] our legal eagle.
1960		Wodehouse Jeeves in the Offing 124: ‘Why, that’s libellous!’ ‘So Upjohn and his legal eagle seem to feel.’.
1971		F.J. Hardy Outcasts of Foolgarah (1975) 61: A snivelling legal-eagle from the bosses’ court.
1985		B. Humphries Traveller’s Tool 3: It will help legal eagles get to the bottom of the endless Royal Commissions.
1992		S.L. Hills Tragic Magic 98: You always thought he was a legal eagle and he ain’t shit.
2005		M.B. ‘Chopper’ Read Chopper 4 95: All the book royalties [...] have already been spent on high-flying legal eagles.
2020		D. Whish-Wilson Shore Leave 20: [T]he studied poise of the Terrace legal eagles, headed into court.