I got fired last year for a positive marijuana test, can I get reinstated now that it's legal

Laws are prospective. They apply from an effective date into the future. It is very rare for a law to be applied retroactively, meaning in hindsight. Have you re-applied for the job you lost? Complete the employment application honestly. Make a copy. Sometimes the questions asked on employment applications are illegal. Some questions may be allowed only after a conditional offer of employment is made to you. If you are not re-hired and are now the most qualified applicant, this employer's refusal to hire you might be illegal if it perceives you as disabled or impaired and you are not. Remember that your specific job duties will determine whether you can perform the essential functions of your job while medicating with marijuana. Like other prescription pain medication, you may not be able to successfully perform the essential functions of your job wit marijuana in your system. Regardless of what your prescription pain medication is, they all remain in your system for some time and many impair functioning while medicated. There may be some jobs where marijuana could be used on-the-job but that will depend on your actual job duties and the position you hold. If you were a surgeon I doubt that the Department of Education or Board of Medicine would permit a surgeon to be under the influence of marijuana (prescription or otherwise) during surgery or before performing surgery. The jobs which allow use may be more limited than we think regardless of whether tests can accurately detect use. Remember that unless your union requires a positive test result before an employee/member's termination, an employer suspecting an employee's performance-altering medicinal use can fire the employee not because the employee is medicating, but because the employee's performance is below the employer's standards, test or no test. Positive tests for drugs or alcohol were rarely necessary to fire employees, even before the law changed. The legality of marijuana use may prevent criminal prosecution of employees in most cases. But if you operate a 70,000 pound tractor trailer on the public highways running 70 mph and your employer watches you consume medicinal marijuana before you jump into your tractor for a cross-country run, and soon after crash into passenger cars causing fatalities, might you and your employer face gross negligence liability and even vehicular homicide charges in criminal court, regardless of whether marijuana is legal in New York?