Not sure whether there is a specific reg dealing with it but..
Any vehicle or aircraft crossing in front of the LOC antenna disrupts the signal. This is especially importand in Reduced Visibility. In my facility guidelines are being published at the moment.
Don't knoe the applicable distance yet, but I expect it will be along the lines of 'Aircraft or Vehicles will NOT be permitted to cross active RWY if ILS inbound is within XX NM'
Landing Clearance usually within 2NM - Less if advised in advance.