If some random stranger parks his car in my owned parking and doesn't

At commercial property we have open parking space at nights we use rope to close the parking area . Other night Inspite of night watchman telling the trespasser , the person parked his car after removed the rope himself . He didn’t turn up for more than 30 hours. Luckily in the day time Tennant didn’t create problem for lack of space to park as this was parked the whole day. Again he turns up in the night and takes his car away. To avoid such situations in future can we use the anti theft wheel clamp and lock the car . Also after having a label mentioning in our premise saying no parking without owner permission . Is it illegal to use the lock while trespassers create nuisance by parking at our space and not returning for hours or day or so . Pls kindly let me know. Thanks in advance .