Without resorting to silly commentary , I'll just say I don't think it's going to work . I do think it's going to cause more problems that it cures .
Before the law:
police - sir, back up, you're interfering with this investigation
bystander (since some people are big on the bystanders having some occupation, perhaps a tug boat captain) takes a step back - no I'm not
police - keep going, you're still interfering with this investigation
bystander takes a step back - no I'm not
police - keep going, you're still interfering with this investigation
bystander takes a step back - no I'm not
police - keep going, you're still interfering with this investigation
bystander takes a step back - no I'm not
After the law:
police - sir, back up 25 feet, you're interfering with this investigation
bystander (maybe this one is an uber driver) backs up 25 feet - no I'm not
I see you're point now. Having an objective standard is much more confusing than having a subjective one.