When I worked in Singapore, Malaysia, Vietnam and Indonesia we looked into this issue fairly closely, for movie film and specifically for 'recans' and short ends. Recans have been loaded into the magazine in case they might be required, then returned to the can entirely unused. Short ends are better known - they are the partially used rolls of film.
In both cases the film has been packed into a bag and then into the can along with some very humid (high relative and absolute humidity) air. The question was: will this cause problems and do we need to use silica gel? We ran through the theory, studied the way in which the moisture moves around as conditions changed and ran a few tests (fairly large sums of money are involved here - not just the value of the film, but the risk of using film that is even slightly damp). Long standing practical experience shows that it is OK, of course, but we thought that it was worth a bit of investigation to see how close to disaster we were.
It isn't an issue at all with film that remains sealed in its original packaging - there is a certain, low, amount of moisture locked in and the conditions outside the sealed container are fairly irrelevant, within limits. There is an issue about the degree of sealing though. The air pressure in the container will change as the temperature changes, and this pressure change may be enough to cause the container to breathe a little. It will breathe in when the container is cooled. Fortunately the air inside a freezer or refrigerator has very low absolute humidity.
Anyway, without going into all the unpleasant thermodynamic details (furnished upon request) we were satisfied that there was no problem re-freezing in this instance, if the film is wrapped in the normal way with little air space in the bag - the bag folded closely around the roll of film. If a short end was wrapped loosely there could be a problem. Including a single pack of silica gel would not guarantee that there would be no problem in the case of a loosely packed film.
So, as long as the film is sealed (and there is very little air sealed in with it) and all the sealing and unsealing operations are done when the film has fully equalised to ambient temperature you can re-freeze film that has been opened in humid conditions. But you knew that already.
Best,
Helen