Yes they can. There is no protection under law for making money off the ineptitude of other companies. Apple is entitled, and expected to fix bugs. When those bugs get fixed, an avenue for jail breaking gets closed. Companies that see their revenue stream dry up are just screwed. That's life.
Jail breaking happens because Apple screwed the pooch on security. That's all.
Thats the problem you missed
restraint of trade,
Apple would take Microsoft or any other company to court in o.0005 seconds if restraint of trade was against them.
Jail breaking is ruled legal by the federal government
Cydia and theme it require Jailbreaking to sell the apps they have.
Cydia and theme it are legally selling apps
Apple then goes after Jailbreaking and restrains Cydia and theme it from doing legal trade
This is not a legal act by Apple, so they say its patching for security reasons ( A lie)
You call it security yet the doorway used to jailbreak the Iphone or Ipad has never been used for anything else then Jailbreaking.
Your using an Apple company tactic of telling us its unsafe, you work for apple or believe the unsupported claims by Apple.
Apple believes it looses money from Jailbreaking because these people now buy from other sources than Apple's app store.
I find it sad that so many believe what ever Apple says is the truth.
Apple is a multi billion dollar company that needs to make money all the time off of you. they need your money and undying loyalty.
( I know people will not agree with my take on this, its fine, I hate big corporations and how they lie to us, look at the Japanese and the lies from the power company, it happens again and again everyday)