Green’s Dictionary of Slang

1. (US) to set the law on, to arrest.

1903		A. Adams Log of a Cowboy 81: They’d have lawed me if I had, but I ought to have shot him and checked the breed.
c.1929		Z.N. Hurston Bone of Contention (1995) 971: Ah wants uh warrant took out fuh Jim Weston. Ahm gointer law him outa dis town.
1948		Z.N. Hurston Seraph on the Suwanee (1995) 700: What is it to be lawing and jawing about, Arvie? It was nothing but children’s doings.
1956		N. Algren Walk on the Wild Side 133: ‘Some nigger drunk pitchin’ glassware.’ [...] ‘Ought to be lawed.’.

2. (UK Und.) to impersonate a police officer.

1957		P. Beveridge Inside the C.I.D. 199: Lawing Posing as police officers.
1959		cited in Partridge DU (1968) 399/2: law v. [...] ‘since late 1945’.
1959		J. Gosling Ghost Squad 67: The villainy became to widespread that the crooks’ word for it went into their argot. They began to talk of ‘Law-ing’ a man: robbing him in the guise of a policeman.