Blood wards are canon, what strongly implies that this is a specific form of magic (wards). This part is a canon.

There are other very similar protections (no apparition at Hogwarts etc) this is also canon.

I would argue that wards are canon.

EDIT: It appears that my memory of canon is worse than I thought and blood wards may be purely fanon, or non-canon creation via interview with Rowling.

 

Unless you've got a page citation for the term "blood wards" appearing in the books, I'm going to lean heavily towards fanon. I couldn't find it when I checked earlier this morning, but I was also dead tired from fighting with my computer all day yesterday.

EDIT: I also believe that Pottermore said something about preventing apparition through a charm and a jinx (one for coming and one for going, though I don't remember which was which). So while there are area effect defensive spells of a sort, whether that makes them akin to fanon's "wards" is another thing entirely.

 

There are certainly defensive spells. Some even protect entire buildings. But they are never called wards. They are just spells, charms etc. Canon never marks out a specific 'ward' niche the way fanon has either, and it certainly never gives it the name 'wards'.

 

They're never referred to as 'wards,' so much as defensive enchantments and 'protections.' Even curse-breakers never seem to use that word, though they're breaking very old, often protective curses.

I would say HP magic makes a point of protecting something specific (Harry, certain objects, information, what have you), or protecting against specific things (physical or magical entry, muggles, maps, other forms of detection etc.), whereas wards (in fanon or other media) tend to act as sort of a catch-all, however powerful, for whatever is coming your way. Wards are made to stop a variety of things, and when they're layered, it's generally to add strength. When HP protections are layered, it's to add variety. A single ward might offer versatile but weak protection, whereas a single HP defensive enchantment might offer very powerful protection, but only in a limited or single way, forcing wizards to know a wider variety of spells than if they simply knew a series of general wards with varying intensities of protection.

This would be why ordinary wizards like Diggle or those at the Ministry were able to find Harry at Privet Drive while Voldemort and his followers could not. Dumbledore did not protect him from visitors altogether (or the Dursleys might have found it hard to live), but from a certain kind of visitor.

 

Others have answered the "wards" part of your post, but there's nothing in canon about the "blood" as being magically potent in and of itself.

The entire point of the Dursleys being blood relations has nothing to do with blood and magic per se, but rather, that the blood that is running through Petunia's and Dudley's veins is a familial connection to Lily. It isn't the blood that gives the charms/spells power, it's Lily's sacrifice of love and the familial relation as represented by blood.

In Voldemort's reincarnation (in the literal sense), it was one of the physical materials necessary for the potion to give him a new body, as the items given were all representative of different parts of the human body: flesh, blood, bone etc.

In the cave when Dumbledore stops Harry from giving blood to get through, there's two issues there. The first is that blood is merely the item used to disarm the spell. Dumbledore even says (IIRC) that it was set that way to weaken physically the enemy that tried to get through. The second issue was that Harry's blood was more . . . precious? I don't remember the exact phrasing. That is the closest that you can get to blood actually having a quality in and of itself worthy to magic. Yet, here I've always interpreted that as allegory for Harry's life being even more important than Dumbledores.

The phrases "Mudblood" and "Half-blood" also speak not to magical potency or ability, but merely to family relations/ancestry.

 

About the blood protection:

[QUOTE="Dumbledore in HP & OotP, Chapter 37" ]“But I knew, too, where Voldemort was weak. And so I made my decision. You would be protected by an ancient magic of which he knows, which he despises, and which he has always, therefore, underestimated - to his cost. I am speaking, of course, of the fact that your mother died to save you. She gave you a lingering protection he never expected, a protection that flows in your veins to this day. I put my trust, therefore, in your mother’s blood. I delivered you to her sister, her only remaining relative.”

“She doesn’t love me,” said Harry at once. “She doesn’t give a damn -”

“But she took you,” Dumbledore cut across him. “She may have taken you grudgingly, furiously, unwillingly, bitterly, yet still she took you, and in doing so, she sealed the charm I placed upon you. Your mother’s sacrifice made the bond of blood the strongest shield I could give you.”

“I still don’t.”

“While you can still call home the place where your mother’s blood dwells, there you cannot be touched or harmed by Voldemort. He shed her blood, but it lives on in you and her sister. Her blood became your refuge. You need return there only once a year, but as long as you can still call it home, while you are there he cannot hurt you. Your aunt knows this. I explained what I had done in the letter I left, with you, on her doorstep. She knows that allowing you houseroom may well have kept you alive for the past fifteen years.”[/QUOTE]


There you have it. Blood wards? Nope. Protection charm sustained and reinforced by blood? Yup.

 

I'm more willing to accept "protection," as long as we realize that it's not the blood itself that has provided it, but rather, it's the vehicle that continues Lily's protection of her son.

 

What it comes down to is the ward stuff in fanon is people misunderstanding or disliking the conceptual nature of the magic in HP. When something is protected, they think there has to be some physical area covered by a ward that's essentially physical but simply can't be seen. In the case of the blood protection, people immediately assume the actual physical blood is what matters and has some part in the magic itself because they miss the point that it's conceptual.

They can't wrap their head around it or just hate it for some reason so they put stuff in to make it more like other magic systems they know about that are more easily understandable. It's a similar situation where people put in magical cores or magical power generation of some form because there has to be magical energy that wizards form spells out of and it has to be that the more of this energy is in them the stronger those spells are. Because that's easy to understand and common in fantasy.

 

Y'know, there's a number of words that I use in my writing that JKR never did. If I mention 'wards' and my readers understand what I meant, I used the right word.

 

Every time someone bring up wards, I smile and remember Bungle in the Jungle: A Harry Potter Adventure. Good times.

 

...
Sorry you lost me.

 

Wasn't she a brazilian chick? I could bet on it.

 

No, no, no... she had a Brazilian.

 

What is a magical disease?

We have heard tell they exist, Dragon pox (Slughorn mentions Grandpa Malfoy dies of it in HBP) and I think a few other off hand mentions.

Do they just effect magial people? If so how? Is magic something that can be infected? Is magic something substantial that can be seen or touched? Most people here subscribe to the Taure view that magic is something that you harness through knowledge, not a reserve you have, so how is it that we have a magical disease.

Do they just effect wizards and if a muggle gets it they just think of it as a really bad or mysterious normal illness?

What makes the disease magical? That it comes from a magical creature? Or that it is resistant to magic? So the magic flu is just the normal flu that mutated to be resistant to what ever healing crap they use on the normal flu?

 

But then how does it only target Magical people? There has to be something about them that would make them susceptible to it and not a muggle.

 

Magic, because it can be passed down, seems to be an inherently physical, genetic quality, even if the mastery of it, or 'wizardry,' is intellectual. In this sense, even though magic is developed and practiced as a function of understanding, wizards are still possessed of the physical, phenotypical(?) quality of being 'magical,' which is, I think, what might make one susceptible to magical disease. How they spread and present, symptomatically, is another matter open to interpretation.