Review this case which deals with public employment and constitutional rights to be free of unreasonable search and seizure. Private employers generally speaking have more freedom to restrict drug use. Assuming you have an employee undergoing cancer treatment who has a prescription for medical marijuana and they are drug tested and come up positive. Can you make a legal argument that they should not be fired?

72 Cal.App.4th 147
RONALD SMITH, Plaintiff and Respondent,
v.
FRESNO IRRIGATION DISTRICT, Defendant and Appellant.
California Court of Appeal, Fifth District
May 17, 1999
OPINION
LEVY, J.--
... Background Facts
Plaintiff was hired by the Fresno Irrigation District (District) in February 1989. The District is an independent state agency responsible for water distribution and flood control. (Wat. Code, § 20570.) During the irrigation season, which generally spanned the months of March to September, plaintiff worked as a ditch tender. Plaintiff was employed the balance of the year as a construction and maintenance worker for the District.
After consultation with representatives of the employees association, the District adopted a "Drug-Free Work Safety Program Substance Abuse Policy" (Substance Abuse Policy) for all of its employees in July 1994. ...
Under the policy, those employees who worked in safety-sensitive positions were required to take random tests for drugs and alcohol. ...
On January 9, 1995, plaintiff was told to report to an independent testing laboratory and to submit to a urine test for drugs. The results of the test were positive for amphetamines, methamphetamines and marijuana.
Plaintiff received a written termination notice on January 13, 1995.
On January 31, 1996, plaintiff filed a complaint for wrongful termination in violation of public policy, invasion of privacy under the California Constitution, and for violation of his Fourth Amendment right under the federal Constitution to be free of unreasonable searches and seizures. ...
B. Overview of Applicable Constitutional Principles
Plaintiff's complaint alleged that the random drug test was a violation of his Fourth Amendment right to be free of unreasonable searches and seizures under the federal Constitution and a violation of his right to privacy under the state Constitution. (Cal. Const., art. I, § 1.) Plaintiff's Fourth Amendment challenge stemmed from the fact he was employed by a governmental entity.
Similar standards govern drug testing under the federal and state Constitutions. ...
The determination whether a particular drug test is constitutionally permissible is derived from a balancing test. ...
Whether a drug test meets the reasonableness standard is " 'judged by balancing its intrusion on the individual's Fourth Amendment interests against its promotion of legitimate governmental interests.' " ...
The parties herein are in agreement that if plaintiff is found to have been employed in a safety-sensitive position, the random drug test which resulted in his termination is constitutionally valid under both the federal and state Constitutions. ...
Under Labor Code section 6401, the District had a legal obligation to maintain a safe workplace. ...
We hold that the District's interest in reducing a substantial and real risk of injury to plaintiff's coworkers justified the random drug test.
Random drug tests have been found constitutional due to:
1. The potential for injury to a patient by a scrub technician whose duties included setting out the proper instruments for surgery and counting sponges before the patient was sutured. (Kemp v. Claiborne County Hosp., supra, 763 F.Supp. at p. 1368.
2. The potential for injury to a patient caused by a drug-impaired medical resident. (Pierce v. Smith (5th Cir. 1997) 117 F.3d 866, 874.
3. The potential for serious harm caused by a drug-impaired teacher. (Knox County Educ. v. Knox County Bd. of Educ. (6th Cir. 1998) 158 F.3d 361, 378.
4. The potential for serious harm caused by a school custodian who tested positive for marijuana as the result of a random drug test of persons in safety-sensitive positions. (Aubrey v. School Bd. of Lafayette Parish (5th Cir. 1998) 148 F.3d 559, 565 ["... the Board's need to conduct the suspicionless searches pursuant to the drug testing policy outweighs the privacy interests of the employees in an elementary school who interact regularly with students, use hazardous substances, operate potentially dangerous equipment, or otherwise pose any threat or danger to the students"].)
These cases demonstrate that it is not the number of persons who could be injured by a drug-impaired worker that determines the constitutional validity of random drug testing. ...
[Plainitff's position had valid safety concerns because] plaintiff operate power tools in close proximity to his fellow workers, [also] he operated heavy equipment near them as well.
...
We conclude that the District's interest in minimizing the risk of injury to its employees outweighs the plaintiff's privacy interests. Therefore, the drug test which resulted in plaintiff's termination was constitutionally valid.