How can what happen? You didn't really specify, I assume you mean people rated about 1400 in it.
You have to be within the rating range when they start. I have some where I've joined 6 months ago or more and my rating has increased since. You can't stop people from improving.
Having never made a tournament I am unsure how this works...
Basically I have come across a few tournaments lately where it will say '<1400' or something to that effect. Then when you enter there are players rated above 2000.
The question is, how can this happen if the rating range is specifically set below that?
It seems a little unfair on players who enter thinking they will be competing against people in their own rating range to then be paired up with such a strong player. If they were looking for that sort of competition they would join an open tournament.
It seems pointless having the rating range option in the first place if they are effectively open tournaments.