What is Deem?

Legal Definition
Deem in law is used to treat something as if it were really something else or it has qualities it does not have.

Deem has been traditionally considered to be a useful word when it is necessary to establish a legal fiction either positively by "deeming" something to be what it is not or negatively by "deeming" something not to be what it is. All other uses of the word should be avoided. Phrases like “if he deems fit”, “as he deems necessary”, or “nothing in this Act shall be deemed to...” are objectionable as unnecessary deviations from common language. "Thinks" or "considers" are preferable in the first two examples and "construed" or "interpreted" in the third.
-- Wikipedia
Legal Definition
To hold; consider; adjudge; condemn. Cory v. Spencer, 67 Kan. 648, 73 Pan. 920, 63 L. R. A. 275; Blaufus v. People, 69 N. Y. Ill, 25 Am. Rep. 148; U. S. v. Doherty (D. C.) 27 Fed. 730; Leonard v. Grant (C. G.) 5 Fed. 11. When, by statute, certain acts are "deemed" to be a crime of a particular nature, they are such crime, and not a semblance of it, nor a mere fanciful approximation to or designation of the offence. Coin. v. Pratt, 132 Mass. 247.
-- Black's Law Dictionary