He's still allowed to be CEO of Mozilla. (Calling a specific job posting a "right" seems a stretch — do I have the right to be CEO of Mozilla? Where are the complaints that I'm being effectively prevented from exercising that right?)

Nothing and nobody forced him to resign. He could've weathered the storm and risked Mozilla's most valuable asset, its goodwill, over his beliefs. It would've been a terrible thing to do to the company and made him a terrible CEO, but nothing stood in his way.

Claiming that someone's rights were violated because he voluntarily quit his job is patently absurd.

Eich was not legally barred from being CEO. He could have chosen not to step down. He could choose to start his own company to be CEO of. He could be CEO of another company.

He will not be barred by the government from doing all of those things. He is not being prevented from exercising his right to be a CEO. He was asked to step down by many people, as is their right, and he did.

If Mozilla changed their mind and asked him to be CEO again he could. If another company asked him he could. Just because no one wants you to be CEO does not mean you don't have the right to be.