Looks like a compression fit valve, you should be able to unscrew the compression nut from the valve, valve will then slide off.
Nut and brass ferrule will still be trapped on the pipe.
Not much copper to work with, so maybe a new compression valve could go onto that same nut and brass ferrule, just clean up any minerals or corrosion with a plastic scotchbrite pad and vinegar.
You could try a puller to remove the nut and ferrule, if you can’t find a valve that mates with existing, or if the ferrule is not in good shape.
You could also maybe rebuild the valve guts, I am not familiar with that brand.