Is παρείσακτος, ον “introduced privately” a verbal adjective derived from παρίημι? Reason I think this may be so is because the aor. act. ppl. of παρίημι is παρείς and because παρίημι can mean avoid, bypass etc.
Not sure about the -ακ- infix though. Are infixes like this sometimes added when forming verbal adjectives?
Yes there’s (-)ακτος and (-)ακτεος (the equivalent of a gerundive), from άγω & compounds, quite prolific as you’d expect. As verbal adjectives they’re formed on the aorist passive (without internal aspiration).