In 1916, she fought a notable case challenging the interpretation of legal provisions that effectively prohibited women from practicing law in India.

Regina challenged this decision at the Calcutta High Court, arguing that the governing legislation, The Legal Practitioner's Act, allowed qualified "persons" to enrol as lawyers, and that the definition of 'person' included women.

[2] Guha's case was similar to comparable litigation fought at the time in the United Kingdom and USA, in Bebb vs Law Society and Bradwell v Illinois.

[1] It was followed in India by a second unsuccessful petition when Sudhanshubala Hazra challenged the prohibition against women practitioners in the Patna High Court.

[1] The act was passed after Guha's demise, but her siblings established an endowment at Calcutta University in her memory to mark its passage, awarding a medal to the student who stood first in the M.A.