Below is a picture from a job posting. They specifically state "No felonies". Does this violate any laws enforced by the Equal Employment Opportunity Commission? Are felons part of a protected class?
Criminal conviction is not per se a forbidden criterion for employment decisions, but it has the potential to be because of disparate impact doctrines, in particular when African-Americans are significantly over-represented in the population of felons. Green v. Missouri Pacific RR explains that it would be allowed to include the fact of having been convicted as part of an employment decision (including the nature of the offense, the nature of the job, and the time since the offense), but it is not a possible absolute barrier to employment.
EEOC has a lengthy guidance on the topic, attempting to spell out how conviction could be legitimately used. Such an ad is facially discriminatory (via disparate impact), but the employer might be able to shoulder the persuasive burden. The guidance presents a number of scenarios where they state that conviction would be an allowed consideration, but all of them include further conditions such as "convicted of a violent crime" or "within the last 4 years". There are federally-regulated security-type requirements whereby certain convictions constitute permanent employment barriers (46 USC 70105: espionage, treason, terrorism, improper transportation of hazardous materials, murder, RICO violation etc. preclude obtaining a Transportation Worker Identification Credential, which can be a job requirement). As far as I can tell, a blanket "no (felony) convictions" preclusion is not allowed, but coupled with other factors it could be. Lacking such qualifiers, there is a good chance that the ad would be deemed discriminatory.