Leaving aside the frequency of the event, how about we look up the rules for your jurisdiction, and then we get a better idea about whether the sitaution you (and/or bluefirebrand) are thinking about qualifies as illegal?

For example, down in Washington State, I'd paraphrase the law [0] as "store owners can't be sued back if they had good evidence and only stopped the person enough to record information." (Note, that's separate from "citizen's arrest", which comes more from common-law precedents than from explicit statue.)

[0] https://app.leg.wa.gov/rcw/default.aspx?cite=4.24.220