No meat AND Walpin has no standing to enforce that section. Congress would have to sue the president I believe. (way over my head). He might be able to get a writ of mandamus.
There is no recourse to a court remedy. This is strictly a political issue. Congress appropriates the funds and also legislates the existence of watchdog agents. If Congress finds the president is out of line, it applies political pressure. If he strays too far, they have the power of impeachment. If the president is a crook, he SHOULD be impeached, disgraced, removed, and barred from future office - all of that is within Congress's power.
Another thought for Talpin would be to file an injunction to halt the business at AmeriCorps because it has no independent oversight, and is pending Congressional action due to the illegal firing of the existing IG.