I believe I do have a constitutional right to vote, yes? Unless, of course, I am - like Michael Vick - a convicted felon.
Vick has no 'right', constitutional or otherwise, to play in the NFL, period - and the level of ignorance displayed in this thread by certain individuals professing knowledge of constitutional rights and the law is highly amusing. Even more amusing is the arrogant condescension they project while demonstrating their own ignorance.
Vick already had a job in the NFL and, through his own actions and consequences, forfeited that job. Discrimination does not apply, or even exist, in this case. In addition to Vick's egregious violations of the NFL's Personal Conduct Policy, the NFL specifically does not allow its players to be involved in any form of gambling, and even first-time offenders risk being banned for life. Therefore, the NFL is well within their legal rights and boundaries should they choose to ban Michael Vick for life.
BTW, armchair lawyer - when an employee is justifiably terminated 'for cause', companies can and often do state that an employee is not eligible for rehire. Vick's extremely fortunate that Goodell has given him an opportunity to redeem the career that Vick himself threw away as a result of his barbaric behavior.
There you go.