As Internet users ask the question: ‘is it legal to let your cat roam freely?’ – I feel obliged to answer it and I will do so very briefly because the answer is straightforward (as at the date of this post). The answer is YES. This applies to anywhere in the world but there are one or two very minor exceptions but these exceptions are growing in number.
I think you will find that in certain cities in Australia (e.g. Sydney?) there are curfews on domestic cats by which I mean they must be kept in between dusk and dawn. There have been proposals in Australia to make it illegal to let your cat roam freely but at present they remain proposals. Australia has a particular regard for their native species and believe that the domestic and feral cat present a genuine threat to the survival of certain native species; hence their attitude towards free-roaming cats.
In America, a significant percentage of cat owners keep their cats inside at all times. This is done voluntarily. There are no laws as far as I’m aware in any state, county or city barring domestic cats from roaming freely outside. However, there is a general trend towards keeping cats inside for their safety. America is more dangerous for domestic cats wandering outside partly because of predators.
Some Americans think that it is crazy to let a domestic cat roam freely outside while many British people believe that it is crazy to keep domestic cats inside and all times! We share the same language but have different cultures.
As the planet becomes more heavily populated with people and therefore more urbanized there will be a gradual trend towards keeping domestic cats inside at all times and that may well lead to making it illegal to let your cat roam freely. Only time will tell.
P.S. Cats love free-roaming but are oblivious to the dangers until it is too late.