Bava Kama 113a
והאמר שמואל דינא דמלכותא דינא
There is a Machlokes Rishonim if Dina D'malchusa is
applicable in a Jewish Malchus.
According to the רמב"ם & רשב"ם D.D. is applicable
even in Eretz Yisroel with a Jewish Government.
According to the ר"ן the land belongs to the Shevatim
and all of Bnei Yisroel, therefore the Malchus has no power
of Dina D'malchusa.
b) Laws that the populace accepted amongst themselves
and are willing to pay taxes because it benefits the inhabitants
even the ר"ן will agree D.D. applies in a Jewish Malchus."
Today with the State of Israel whose government is non-Frum,
a) Harav E. Henkin & Harav Ovadya Yosef zt"l, all the laws
(not opposing Torah) must be followed because of D.D.
b) Harav Y.S. Elyashiv zt"l, held it is a Safek*
c) The Chazon Ish holds there is no D.D. in
Most Poskim would probably agree,
1) D.D. is applicable on traffic laws and building codes etc.
2) Those who benefit from the social programs may not
cheat on their taxes.
*The אבני מילואים אבהע"ז כ"ח & חת"ס יו"ד ב' שי"ד
both argue on the בית שמואל כ"ח:ג and hold
D.D. is דאורייתא , therefore might be a