Alexander v McKillop & Benjafield 43 SCR 551 (1910), a decision of the Supreme Court of Canada, discussed the effect of a caveat as follows:
"This machinery was designed for the protection of rights, not for the creation of rights.
"
A caveat prevents any disposition of his title by the registered proprietor in derogation of the caveator's claim until that claim has been satisfied or disposed of, but the caveator's claim must stand or fall on its own merits.
"If the caveator has no right enforceable against the registered owner which entitled him to restrain the alienation of the owner's title then the caveat itself cannot and does not impose any burden on the registered title."
Or
Stephens v Bannan & Gray 5 WWR 201, that a caveat is:
"... nothing more than a caution and
an effective notice of a claim of title grounded upon something else and preventing any change in the rights of the caveator by dealings with the land subsequent to the lodging of the caveat."
http://www.duhaime.org/LegalDictionary/C/Caveat.aspx