Not positively, absolutely thief proof, but my Atlas fork stop plate has a drilled hole with a corresponding hole in the base of the triple tree. When aligned hard left a padlock can be attached, and in the hard left condition, working the lock hasp with a grinding tool will be difficult; cutting with bolt cutters impossible.
Nothing prevents the bike being picked up by two or three strong guys and carried off. Happened to me once .... I found the bike in my driveway . I knew some of the big guys were up to some joke, and the fact that I did not freak out when I left the party, deflated the perpetrators.
Slick