You don't really even need legislation. Most produce you buy from the supermarket are from F1 Hybrids [1] which if you plant the seeds are highly variant and lack vigor (i'm not sure of the % of tomatoes in supermarkets are F1s specifically though). This is one natural way things like this have not come to reality and one way most seed producers (especially ones focused on commercial use) use to protect their varieties.
Agreed. You can't generally won't get the same plant from a commercially produced tomato. Instead you will get all kinds of random stuff. Some of it may produce good tomatoes, some may not.
If you are going to go to the effort of growing a garden it's probably worth spending a buck or two and getting some Heirloom or open pollinated seeds. These will breed true and you can replant the seeds from the fruits and get the same plant as the parent.
[1] http://en.wikipedia.org/wiki/F1_hybrid