One such cause is "banning the box," an effort to prohibit employers from asking whether applicants have a criminal record and using that information in the hiring decision. James Jacobs has this guest post at the Volokh Conspiracy:
Hawaii, New York, and Wisconsin make employment discrimination against ex-offenders (CBED) unlawful, unless an employer can show that successful performance of the job would be jeopardized by a person with a propensity for the kind of crime for which the job seeker had previously been convicted.* * *The New York statute and similar anti-CBED laws and proposals are simplistic. It is a mistake to assume that an employer always or usually hires someone only to fill a narrowly prescribed job. Employers routinely want to hire individuals who can fill various positions as needed and who have a chance of advancing through the firm. In addition, an employer wants employees who are honest, rule-compliant, reliable, and self-disciplined, employees who come to work every day and on time, get along well with fellow employees and clients, and contribute to a harmonious working environment.
The New York statute says that an employer cannot base a conclusion that a job applicant lacks good moral character on the basis of previous criminal convictions. Is it wrong to make a moral judgment about a person who tortured animals or brutalized a child or old man? In reality, we regularly reach conclusions about the character of those with whom we interact on incidents and evidence far less reliable than a criminal conviction. Is it okay for an employer to find that a job applicant lacks good moral character based upon a negative or lukewarm reference from a prior employer? A disturbing job interview?The New York statute assumes that offenders are criminal specialists who present specific types of risk, i.e. a sex offense conviction indicates only a sexual threat and drunk driving convictions indicate only a vehicular threat? Research shows that many criminal offenders are generalists and opportunists. Today's burglar was yesterday's drug dealer. The person who today was charged with assaulting his girlfriend yesterday used a stolen credit card.
The New York statute imagines an offender with a single aberrant conviction. Of course, there are individuals who meet that profile, but there are also many offenders with multiple convictions, not to mention multiple, arrests, charges and pre-trial diversions. The statute also ignores context. Should an employer be forbidden to consider the fact that the previous (single) conviction arose out of gang or organized crime activity?

In my capacity as small law firm proprietor, I have sometimes wondered to myself whether I'd hire an ex-con. Obviously, some amount of people do their time and learn their lesson but the issue is for me I have no idea how I could figure out if any random person was reformed or not.
For a small business the consequences of making a bad hire for any reason can be pretty severe because there aren't enough personnel to pick up the slack. Therefore, it is a risk I just can't afford to take. If I was running a larger company it might be something I'd consider but I don't think a person's criminal history should be prohibited as a valid job screening.
I would make one exception to my above statement and it is what I call the "Nazi Rocket Scientist Exception" If an ex-con had some sort of extremely valuable and unique skill-set, I'd strongly consider hiring said person. Realistically, probably not applicable in my line of work.