Yeah, could be parking the van overnight is against the company's lease, in which case you've got an easy way to deal with the problem without it being anyone's fault!

Some places will let people park overnight though (Walmart is the best-known example, around here a lot of churches and small businesses will if it's someone known to the church) & if he's in the kind of industry that valorizes things like "van life" and bad work-life balance, he may even have been given enthusiastic permission to park the van & maybe even use the bathrooms. If he's got official OK on the van, getting him out of the building at night will be tougher.