As a state representative, in 1919 he led a state investigation into the Texas Rangers, who had been accused of crimes and abuses in the Rio Grande Valley, and along with the US 8th Cavalry, were involved in the Porvenir Massacre in deep west Texas on the west side of the Sierra Vieja, north of Candelaria and Ruidosa.
The committee heard testimony from 83 witnesses, who revealed extensive abuses by the Rangers of minorities and other poor citizens.
After his service in the State House, Canales continued his work as civil rights activist through several Hispanic and Latin American organizations.
[2] He was a descendant of José Salvador de la Garza, who once held a Spanish land grant encompassing much of present-day Cameron County.
[4] During the decade of the Mexican Revolution 1910-1920), revolutionary raids across the border damaged American ranches, irrigation systems, railroads and other infrastructure.
[2] In 1917 he helped gain passage of legislation preventing Mexican migrant workers from draft evasion in the United States, shortly before the US entered the Great War in Europe.
[2] Canales was an outspoken critic of the Texas Rangers force, who retaliated against raiders and had sometimes acted as vigilantes along the border, especially against people of Mexican descent, citizen and migrant alike.
[2][5]: 73 A joint committee of the state Senate and House was set up to investigate the actions of the Texas Rangers, with hearings to be held in early 1919.
Before the hearings, in December 1918 Canales was directly threatened by Frank Hamer, a noted Ranger, and he reported this to Governor William P. Hobby.
[6] The 1919 Canales investigation, as it became known, heard testimony from 83 witnesses over a period of two weeks, including Anglo, Hispanic, and African-American Texans, and Mexican migrants, who recounted abuses by Texas Rangers.
Incidents included the Porvenir massacre in January 1918 of 15 unarmed ethnic Mexicans near the border, whom the Rangers rounded up from their settlement.
Restrictions were added to reduce Texas Ranger vigilante actions against Mexicans and Tejanos in the Rio Grande Valley, and provide for citizen complaints.