Becasue if the Marijuana Policy Project believes that people should get tested for cannabis use then so should the NFL player, hell it´s clearly in the law (Amendment 64) which Marijuana Policy Project wrote.

(6) Employers, driving, minors and control of property.

(d) NOTHING IN THIS SECTION SHALL PROHIBIT A PERSON, EMPLOYER, SCHOOL, HOSPITAL, DETENTION FACILITY, CORPORATION OR ANY OTHER ENTITY WHO OCCUPIES, OWNS OR CONTROLS A PROPERTY FROM PROHIBITING OR OTHERWISE REGULATING THE POSSESSION, CONSUMPTION, USE, DISPLAY, TRANSFER, DISTRIBUTION, SALE, TRANSPORTATION, OR GROWING OF MARIJUANA ON OR IN THAT PROPERTY.