In the most crime ridden spot in the country, our nation's capitol, District of Columbia Law 23- 582(b) reads as follows:
(b) A private person may arrest another -
(1) who he has probable cause to believe is committing in his presence -
(A) a felony, or
(B) an offense enumerated in section 23-581 (a)(2); or
(2) in aid of a law enforcement officer or special policeman, or other person authorized by law to make an arrest.
(c) Any person making an arrest pursuant to this section shall deliver the person arrested to a law enforcement officer without unreasonable delay. (July 29, 1970, 84 Stat. 630, Pub. L. 91-358, Title II, § 210(a); 1973 Ed., § 23-582; Apr. 30, 1988, D.C. Law 7-104, § 7(e), 35 DCR 147.)
As long as Shelby maintains the holds, he's engaged in an act of extortion against the government. That's close enough to probable cause for me.