It is considered discriminatory hiring practice if they do unless it is under certain circumstances, this changed when it was legalized. They shouldn't even be testing for THC unless it is for specific positions. If they don't hire you based on that and it is not one of the under conditions they are participating in prohibited hiring practices and if they are not following these laws who knows what else they might not be following.

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21-28.11-29. Prohibited activities.

(d) Nothing contained in this chapter shall be construed to require employers to

accommodate the use or possession of cannabis, or being under the influence of cannabis, in any workplace or the use of cannabis in any other location while an employee is performing work, including remote work. Employers may implement drug use policies which prohibit the use or possession of cannabis in the workplace or while performing work from being under the influence of cannabis, provided that unless such use is prohibited pursuant to the terms of a collective bargaining agreement, an employer shall not fire or take disciplinary action against an employee solely for an employee’s private, lawful use of cannabis outside the workplace and as long as the employee has not and is not working under the influence of cannabis except to the extent that:

(1) The employer is a federal contractor or otherwise subject to federal law or regulations such that failure to take such action would cause the employer to lose a monetary or licensing related benefit thereunder; or

(2) The employee is employed in a job, occupation or profession that is hazardous, dangerous or essential to public welfare and safety. If the employee’s job, occupation or profession involves work that is hazardous, dangerous or essential to public welfare and safety then the employer may adopt and implement policies which prohibit the use or consumption of cannabis within the twenty-four (24) hour period prior to a scheduled work shift or assignment. For purposes

of this section, hazardous, dangerous or essential to public welfare and safety shall include, but not be limited to: operation of an aircraft, watercraft, heavy equipment, heavy machinery, commercial vehicles, school buses or public transportation; use of explosives; public safety first responder jobs; and emergency and surgical medical personnel.

(e) Nothing contained in this chapter shall prevent an employer from refusing to hire, discharging, disciplining, or otherwise taking an adverse employment action against a person with respect to hire, tenure, terms, conditions, or privileges of employment because of that person’s violation of a workplace drug policy or because that person was working while under the influence of cannabis.

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https://www.littler.com/publication-press/publication/employer-drug-testing-rules-clipped-rhode-island-marijuana