Unless
If you're not 14 years old, you must be with an adult to go go-karting.
Unless you're 14 years old, you must be with an adult to go go-karting.
If it doesn't snow, the mountain will be closed for snowboarding.
Unless it snows, the mountain will be open for snowboarding.
or
Unless it doesn't snow, the mountain will be closed for snowboarding.
You can't go sailing if you're not in a group.
Unless you're in a group, you can't go sailing.
If you've never been horse riding, you need to go with a guide.
Unless you've been horse riding, you need to go with a guide.
If you don't know how to swim, you're not allowed to go canoeing.
Unless you know how to swim, you're not allowed to go canoeing.
You can't go rock climbing if you don't wear a helmet.
Unless you wear a helmet, you can't go rock climbing.