Beginning of the Texas Constitution(I confess I have not read since civics class decades ago):
ARTICLE I
BILL OF RIGHTS
That the general, great and essential principles of liberty and free government
may be recognized and established, we declare:
Sec. 1. FREEDOM AND SOVEREIGNTY OF STATE. Texas is a free and
independent State, subject only to the Constitution of the United States, and
the maintenance of our free institutions and the perpetuity of the Union depend
upon the preservation of the right of local self-government, unimpaired to all
the States.
Sec. 2. INHERENT POLITICAL POWER; REPUBLICAN FORM OF
GOVERNMENT. All political power is inherent in the people, and all free
governments are founded on their authority, and instituted for their benefit. The
faith of the people of Texas stands pledged to the preservation of a republican
form of government, and, subject to this limitation only, they have at all times
the inalienable right to alter, reform or abolish their government in such manner
as they may think expedient.
In its Constitution, Texas has declared itself a free and sovereign state, only subject to the US Constitution.
But that US Constitution must be followed by the federal government as those are the conditions upon which entry was made. When it is not followed, Texas remains free to declare so as the agreement has been abrogated.
That us nullification, and remember the federal government is not a party to the US Constitution, only the states are.
