The qualification criteria are normally decided upon by the law enforcement bureaucracy under the authority of the executive at the municipal/state/federal level. While legislators can theoretically pass laws that outline specific qualifications, they're unlikely to do so because the subject is complex enough to exceed their expertise.

You might also consider that the qualifications are likely the wrong place to address any problems you have. Individual law enforcement officers have no more say over the policies of law enforcement than the cashier at Walmart can help you if you have a problem with how Walmart does business. It's just that as the most visible representative, both the LEO and the cashier bear the brunt of your rage rather than the appropriate targets.