i personally do not allow my cat outside, and i never have. i love my Squirt too much and am completely paranoid of him getting hurt or just losing his way home. He is now 11 and knows no different but to be inside. He is curious of the outside, as all cats are. But once he is out there, he realizes it is not the comfort of his own home and immediately wants back in. Eventually your cat will get used to it. You may have to put up with his meowing for a week or two, but it will be worth it in the end. Water bottles work great for teaching cats what they can and cannot do. If he is meowing at the door, spray him with a water bottle. He will learn quickly that he is not allowed. And no, using a water bottle is not mean. It is a type of reinforcement that really worked on my cat.

-Khoyman