You can use "Drun" (to bring, make happen) and "Nis" (can't). For instance : "The guardian prevents the thief from escaping" could be : "Deinmaar drun tafiir nis filok".

I would offer this: "Stop!" can be "Ni bo!" (Don't go) or "Vobo!" (Un-go!) or "Saraan!" (wait). 

Kahvozein's sample sentence "The guardian prevents the thief from escaping" can be translated as "The guardian defeats the thief's escape" or "(Fin) deinmaar viik (fin) tafir filok." or literally "The guardian defeats the thief escape".

Alternately (maybe not recommended):   You can use "vo" (undo) and say "Deinmaar vo fin tafir filok." (The guardian undoes the thief's escape."