Can he sue?
Malicious Prosecution
False Imprisonment
Violation of Civil Rights Under Section 1983.
He can get his money back plus actual monetary damages & punitive damages too.
I hope he includes obama.
President obama discussed Flynn probe with Comey at White House meeting
https://www.washingtontimes.com/news/2020/may/7/president-obama-discussed-flynn-probe-comey-white-/