This is a tricky one. Yes, you can collect resumes, and although not typically a best practice, it can be done with some planning. The best thing to do is probably to encourage visitors at a job fair to apply using the same system everyone else does. If there are particular jobs that you are looking to recruit for at the fairs, then you may be able to limit your applicant pools. Make sure that you have a system in place - what are the qualifications, are there any data management techniques the company can use to manage large numbers, for how long will the company hold that resume, etc. I would not recommend that resumes be collected without a specific plan in place and of course, it is best to keep an eye on analyses to ensure there is no impact against a particular group. As you are probably aware, it is typically not a good practice to collect resumes and consider for a variety of jobs.
You can use this OFCCP audit checklist to ensure you're doing what is required to maintain OFCCP's regulations including VEVRAA, Section 503, and EO 11246. Or request a demo to streamline your compliance and recruiting efforts.