
Some of the answers on here are a weeeee bit scary...
Hes being a brat, you are asking him to do something and he is saying No.
Why is he saying no. Is he saying 'No,what im doing right now is nicer', is he saying 'No I do not understand what you mean', is he saying 'No, your manner/body language/tone frightens me' (or even 'no, you say one thing but your body language says PLAY PLAY PLAY' especially wrt not coming inside).
Regardless of the size of the dog, what kind of 'no' he means - arguing with him isnt going to work. Hes faster, hes got bigger teeth, and sharper reactions. Escalating the issue and getting more domineering with him will make him reciprocate. Aggression begets agression.
Set things up so you avoid these arguments in the first instance.
Put toys away before he goes outside. Use a long leash and teach him that going outside means he goes to the toilet first and plays *with you* afterwards. No toilet, back inside he goes. If possible, split the garden so kids have one part and dog has the other so there are no toys out there for him to get hold of.
With my deerhound if shes being a madam (and she can be) and wants to stay out and ideally... wants someone to come out and chase her, she ignores a recall and loiters near the back door, out of sight from the kitchen door or kitchen window. I wont go out and fetch her, thats playing right into her sneaky little paws - if she doesnt come in when asked i shut the doors and do something noisey and involving biscuits iwth the other dogs. Within seconds there is a deerhound knocking at the door wanting in!
(And if she wants to play outside on her own, since theres none of my stuff out there and shes trained to toilet first, play second, I dont really mind, i just wont stand there with the door open freezing my bum off!)
Also question - does he get enough time outside playing? Deerhound madam unfortunately missed out on a lot of puppy play because of a knee injury and so that is what triggered this 'wanna stay out come chase me' lark. A few months down the line and shes far better as now we do play outside with her every day.
Keeping items you dont want stolen away from a dog, and walking away from him whenhe has something and starts the 'ive got your xyz and you want it chase me and lets have a row about it' saga - and going and doing something else that HED like to be involved with works wonders.
As for the sofa - use a baby gate or close the door if you arent in that room. If you are using that room I would make a point of asking him to do something else if he is on the sofa, not just commanding him 'off' because that gives him the option to say 'no. shant'... and you are back in the argument again.
Instead ask him to come with you and have a game with a squeaky toy, or do some sits for a treat, or pick the lead up and go for a quick clicker session in the front garden/street... ask a question hes likely to say yes to!
Make a point when its less of an issue, of inviting him onto the sofa when you are on there, and inviting him off again for rewards. Your sofa... it can be shared by invitation (or polite request).
Physically dragging him off by his collar is a seriously bad plan. Its just teaching him to up the ante and to expect that when hes in a comfy place on teh sofa hes going to get dragged off (which isnt nice and hurts) and that when he says 'no' you will say 'well ill force you' to which he says 'then ill say no louder' and then you say 'bring it on' and then he says 'ok ill bite you'...... and then he gets put down... (or maybe not then, but maybe when aunty betty reaches out to pet him when hes on the sofa and he thinks 'oh crumbs heres that argument agian oh ill just bite her, they never listen'...maybe then he does!).
Of course - there are times when someone cannot understand why their dog has such a thing about the sofa - and then you realise the dog has NO comfy bed of his own in a suitable place.. or he has a bed but its tucked away where he cant see anything so doesnt feel safe there, or its in a draught and is horrid to lie on.... so make sure thats not a problem, otherwise you can hardly blame him for wanting a comfy secure spot with a good view of doorways and out of the draughts! (Not saying that is you.. but interestingly my ancient saluki always had to sleep on the sofa, until i bought a beanbag bed which is high enough so its out of the draughts, snuggly so she feels safe and still gives her a view of the doorways and isnt right on floor level where she might get stepped on which is one of her big 'things'... *doh*... took me five years to think of that!)
NILIF has its benefits.... but all too often i find that Nothing In Life Is Free often translates to 'Everything Is Really Expensive and Rare'..... and as such interaction and attention are meanly rationed and the price the owner expects the dog to pay is too high, and it becomes yet another 'me human, you dog' domination situation again.
If 'Nothing In Life Is Free - But Shopping Opportunities and Bargains are Frequently Available' then thats fine, but do be wary of harsh programs that deny your dog the right to ask for your attention politely or suggest a game or a cuddle - thats not a nice relationship to be in at all. All too often 'dominant, attention seeky dogs' are bored witless and have no other way of getting ANY attention. Harsh NILIF programs on these dogs make them worse.