Why might it be difficult for laws enforcement officials to discover and prevent illegal inhalant use?

It might be difficult because inhalants can be found just around the household. Gasoline is commonly found in garages, cleaning materials, spray paints, paint thinner, rubbing alcohol, alcohol. If they ban inhalants, or 'illegal inhalants,' it is almost impossible to ban those general household items that can be necessary for jobs, hygiene and eating. 

Try tylenol or see a professional