Can my employer legally fire me while on restricted duty, due to an injury I sustained while on the job?

In many circumstances, yes--the employer can fire you while you are on restricted duty due to an on-the-job injury. For example:

1) You can be fired for unrelated good cause, such as violating company policy, not following supervisor instructions, falsifying time or expenses, etc.

2) You can be laid off as part of a restructuring, down sizing, RIF, etc.

3) If you cannot do your job anymore, and have used up all FMLA (or similar state) leave and/or all paid time off--the employer is not required to retain an employee who cannot do his or her job.

So while the company cannot fire you due to your injury--and may in many cases be required to make certain reasonable (i.e. not too expensive or disruptive) accomodations to allow you to do the job, if you just need some assistance or a slight change in how the job is done--it can still fire you for unrelated reasons or if you, even with reasonable accomodations, can't work and have run out of leave or paid time off.